I looked it up and it seems to use floating point math so it seems to do a decent job with XP up to a point :p
Take normal XP and multiply it by 251 ... then add zone modifier and numbers start to hit the billions but AAXP is calculated as a UINT32 .. so just over 4billion AAXP allowed?
mlevel *mlevel * 75 * 35 /10 = MonsterXP
XPMOD = 100 + spellbonus
MonsterXP * (XPMOD /100.0f) = XPafterMod ------ (Luckily this part is floating point math otherwise it would break here lol)
(ez doesnt use racial mods and such)
RuleValueAAXPmod * XPafterMod * zonexpmod = AAXP
AAXP is where the number gets HUGE -- since i dont know the EZ RuleValueAAXPmod or zonexpmod for certain zones I cant calculate it very well =p
But doing a few test level 80 mobs the numbers were getting very very close to breaking the limit with 25,000XP spell