How many Irish fans with tickets for Croatia game?

With 10,000 official Irish tickets and 10,000 official Croatia tickets, what are the estimates on how many other tickets have gone into Irish hands?

I've heard figures like 20 - 25,000 banded about for the trip. If there was 20,000 Irish in the stadium - that would mean 10,000 of the remaining 25,000 non Croatia or Ireland tickets would be Irish - basically a home game for Ireland!

I know these figures are exaggerated by media usually, but based on hearsay how many Irish have bought off portal/other means do we think?

I'd estimate about two thirds of the stadium was Irish last night, attendance was given as 39900, so around 25000 - 27000 Irish.