Last season, it was 11mm. This season, could the difference prove to be just 21 seconds?
Premier League 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 rather different at Anfield.
Just five minutes and five seconds in, City were convinced they should have had a penalty awarded for handball as Bernardo Silva's cross struck Liverpool right-back Trent Alexander-Arnold.
A mere 21 seconds later, they were behind.
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.
Immediately City protested as on-field referee Michael Oliver waved play on, but the hosts quickly put the incident behind them as they charged up-field.
The result?
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."
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 verdict after the match.
So what did the referees have to say?
The decision 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 hand-ball 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."