ffxiv-datamining/research/quest_exp_reward.md

Quest experience points are generated using a small equation. Why this is done I am not sure as the values always seem static.

(base * paramgrow * (45 + 5 * level)) / 100;

The base value can be found in the quest itself, offset: reward_exp_bonus found here

The paramgrow value is found in the ParamGrow file! offset: exp_mod found here

The level is the level of the quest, offset class_level_1 (main class) found here

If a quest is a bove 50, it has an additional 10k exp per 100th base value.

So after the question, you would do:

exp + (base / 100) * 10000;

Not fully confirmed this, but it has worked for a few 50+ quests I tested against.