why i cant receive exp on mobs 11 lvls above or below me. how to change it?

because that's retail like check calculateExpAndSp() on attackable.java

private double[] calculateExpAndSp(int charLevel, long damage, long totalDamage) { final int levelDiff = charLevel - getLevel(); double xp = 0; double sp = 0; if ((levelDiff < 11) && (levelDiff > -11)) { xp = Math.max(0, (getExpReward() * damage) / totalDamage); sp = Math.max(0, (getSpReward() * damage) / totalDamage); ................