May you need to put less experience on "Server/data/xml/stages.xml" or if it's disabled, you can find it on your config.lua file, some line like this:
Lua:
-- Rates
-- NOTE: rateExp is not used if you have enabled stages in data/XML/stages.xml
rateExp = 5
Code:
<?xml version="1.0" encoding="UTF-8"?>
<stages>
<config enabled="1" />
<stage minlevel="1" maxlevel="99" multiplier="800" />
<!--
This mean if a player kill a monster from level 1 to 99 the player will take x800 expierence
a rat gives 5 of experience, but with this multiplier the rat gives 4000
-->
<stage minlevel="100" maxlevel="199" multiplier="200" />
<!--
But in this case if the player grow up in level, (100 to 199) the player will take x200 expierence
a rat gives 5 of experience, but with this multiplier the rat gives 1000
-->
<stage minlevel="200" multiplier="5" />
<!--
And in this case the player of level 200 or more, will take x5 expierence
a rat gives 5 of experience, but with this multiplier the rat gives 25
-->
</stages>
And if there are more than 5, may you need to put less multiplier, this means that monster gives 5 times more exp than monsterName.xml file says, ex.
In "server/data/monsters/demons/demon.xml" there are a line that means how many experience the demon will give, in the normal case the exp of demon are: experience="6000", but with this miltipliers, this means the demon will give experience="35000".