This is out of the air, so someone will probably be able to correct, but I thought I'd heard ages ago that it was 30% of the days winning time.
(although it's not a hard and fast rule, whatever it is)
The time limit is worked out based on the categorisation of the stage, so less on flat days, a larger percentage on mountain stages. Would think it's 120% of the winner's time today.
Talansky is a trooper, but he'll do well to make the time limit.
cool, cheers