Yes, QuestExplow = {20,25,30,40,50}, and QuestExpmax = {4020,5025,6030,8040,10050},
Can be adjusted to whatever you like. Basically, the low number is the reward for 1 star quests and the max numbers are for 5 star quests. It's base values, which then get multiplied, depending on character level in some unknown formula. Just make sure you never make the low number higher than the max number. If you do, it will cause an overflow and give you like 2 billion XP the moment you turn in a quest.