Daylight should be the bar for a VAR overturn (I.e. clear and obvious). Any part of the player is clearly onside then it's not overturned.
People say offsides are factual and not subjective. It's not though if it takes 5 minutes to make a decision.
No, offside is not subjective, its factual, its written in the law:-
A player is in an offside position if:
any part of the head, body or feet is in the opponents’ half (excluding the halfway line) and
any part of the head, body or feet is nearer to the opponents’ goal line than both the ball and the second-last opponent
The problem is, and I expected better from him, that Colina wanted the law applying with no leeway, so that is why they go down to the mm. It takes so long because they have to then check to the mm, they're not allowed to be unsure, they have to be spot on (impossible but there you go) this is where the issue is arising.