I assume this is a bug since in the two other mods I play I can recruit all of the prisoners.
So, let's say I am fighting a battle against 30 Robber Knights, I have an army capacity of 270 and 130 men, the Robber Knights have 70 prisoners, about 30 of which I really want, the rest I would recruit and give to the Night Watch because I am heading up there, but after the fight, only 20 or so prisoners, normally 1 of each type, like 1 Reach Rider when they had 10 prisoner show up. As I say, in the other two mods I play it doesn't work this way, so is this a bug? I should get to pick from ALL the prisoners of an army I just beat in the field.
You may be having this issue http://aworldoficeandfire.co.uk/Forums/index.php?topic=37807.15 There is an example of how to fix it manually on the 2nd page.