That player will have been above 2500 eventhough both before and after the tournament he was below.
The website you link only shows what the rating was at the start of each month. He is very close to 2500 on those. But apparently at some point in the middle of a month he must have been above it.
When one of the requirements is to have or reach 2500 Fide Elo rating
https://ratings.fide.com/profile/2093596/chart