The Global Stats page appears to be drawing its numbers from the total number of players in Regular and Hardcore mode that are reaching Immortal status, instead of just the former.
http://www.funtrivia.com/minigame/globstats.cfm Challenge Status
There are currently 75 players who have reached level 10 and become Immortals.
The global challenge comes to an end if this number hits 100.
There are currently 15 Immortals who have never won the Immortal badge before.
The global challenge comes to an end if this number hits 30.
There are currently 4160 players participating in this challenge.
There are really just over 60 players who have reached immortal in regular play, (and the number that counts is really 45 if you remove the ones who have reached it for the first time). Right now, it looks like it will end much quicker than it probably will, if the returning HC Immortals are not going to be counted in the 100 limit.
Thanks,
Sue