Last season, it was 11mm. This season, could the difference between winning the Premier League title and missing out prove to be just 21 seconds?
Leaders Liverpool opened up a nine-point gap on champions Manchester City on Sunday, as Jürgen Klopp's side ran out 3-1 winners.
But it could all have turned out very differently at Anfield.
Just five minutes and five seconds in, City were convinced they should have had a penalty for handball as Bernardo Silva's cross struck Liverpool right-back Trent Alexander-Arnold.
A mere 21 seconds later, they were behind.
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What happened, exactly?
After a breathless start, Silva whipped a cross from the right into the box towards the waiting Sergio Aguero.
With Alexander-Arnold his closest marker, the Liverpool right-back got caught in an awkward moment as the ball popped up to strike his right arm.
City immediately protested as on-field referee Michael Oliver waved play on, but the hosts quickly put the incident behind them as they charged up-field.
Fabinho drilling in a wonderful strike from 25 yards to send Klopp's men on their way following a potentially season-defining 21-second period of play.
After the match, Alexander-Arnold told Sky Sports: "I think it might have hit my arm but it hit Bernardo Silva's first. You have to carry on playing, they complained but you have to keep on playing."
Meanwhile, former City captain Kompany argued play should have been stopped in the Liverpool box, regardless of the final verdict.
He told Sky Sports: "You can argue about Bernardo's handball before - I don't think he knows anything about it and it's a natural position. But [Alexander-Arnold's] is a handball, that's not a natural position. Stop the action then and make a decision.
"You go which way you want to go, but my interpretation is that Bernardo's hand is in a natural position and Alexander-Arnold's isn't."
What happened last season?
Cast your mind back to 3 January, as Liverpool arrived at Etihad Stadium looking to open up a 10-point gap over Manchester City at the top of the Premier League.
With the game goalless, Sadio Mane struck the post and John Stones' attempted clearance rebounded off goalkeeper Ederson, forcing the defender into a dramatic last-gasp clearance.
Goalline technology showed the ball was just 11.7mm short of crossing the line.
Pep Guardiola's side went on to win the match 2-1, condemning Liverpool to their sole defeat of the season as City eventually claimed the title by a single point in May.
'What a load of rubbish!'
"Ask to the referees, don't ask me. Ask to Mike Riley and the guys in VAR," said Guardiola on the decision after the match.
So what did the referees have to say?
The call not to award Manchester City a penalty was, according to the Professional Game Match Officials Board, because the appeal for handball against Trent Alexander-Arnold "did not meet the considerations for a deliberate handball".
That explanation did not sit well with all.
"What a load of rubbish! Absolute drivel," said Radio 5 Live pundit Chris Sutton as he was read the statement.
"If I was a Man City player I'd be furious. In games that are decided by such tiny moments, that was a refereeing howler."
Sutton added: "There will be controversy. It did look like Trent's arm was in an unnatural position. I think Alexander-Arnold is a lucky lucky boy. It should have been a penalty.
"I don't understand why it wasn't given. His arm was out, it hit him on the arm - it's a penalty. I just don't get it, with what we have been told about the handball rule that has to be the definition of a penalty.
"Why on earth does Michael Oliver not take it upon himself and look at it on the monitor? Later on he will see that decision and know that he got that wrong."
Robbie Savage, also speaking on BBC Radio 5 Live, added: "How on earth is that not handball? It's absolute nonsense. Go and use the pitchside monitor - it's a big error."
Perhaps predictably, many foresaw the role VAR would inevitably play in Sunday's heavyweight clash.
Over on the BBC Sport live text, the VAR prophecy came true.
Liverpool were ultimately able to run away with the game. Mohamed Salah doubled the advantage before half-time, with Manchester City undoubtedly still reeling from the early turning point as the Blues' assistant boss Mikel Arteta was pictured in deep discussions with fourth official Mike Dean as the teams emerged for the second half.
Sadio Mane's goal then sent City three behind in a Premier League game for the first time since January 2018 - which also occurred at Anfield - and Silva's late glimmer of hope was not enough to stir the visitors to a dramatic late fightback.
Or prevent Guardiola from some rather sarcastic 'thank yous' as he marched over to the officials at full-time.
With the champions languishing in fourth behind Brendan Rodgers' Leicester and Chelsea, can anyone now prevent Liverpool from claiming their first Premier League title?