Bestiary Needs

When you go into your Clan Primer and check out your Bestiary, there is a countdown number under "Needs" that obviously decreases as you defeat teh certain number of enemies.

My question is, what is it for? I've reached the required numbers for quite a number of the enemies now, and I see that an additional page of information is then added to that character about either the enemy or info about the game, but what's the purpose of this? Just to expand our knowledge on what's going on in Ivalice?

Yep. Defeat the number of foes required and you'll get some additional information. It can be information from general knowledge about lands and places; to secrets about items, monsters, and locations.

Like Ichimonji said, this pretty much works like FFX Capture Quest (Monster Arena)