Flain recently asked Flor how exactly Mana Crystals work during training. When you train near them, your mana core slowly draws mana from them. So when you stop training, mana won't leak from the Mana Crystal anymore.
That's absolutely great because if it were the other way around, he'd be wasting Mana Crystals just because he has to attend lectures, and if he started using one, mana would leak out of it needlessly, which would subconsciously make Flain nervous.
Meanwhile, an hour of training had passed, and Flain was curious how much EXP he would get. During the training, he didn't feel anything special—just a normal training session that he knew by heart.
[+360 EXP]
When Flain saw that, his mood instantly improved. Normally in this room, he gets 180 EXP, so this is double. There are two possibilities for what Mana Crystals could be doing: either they give an extra 180 EXP with every training session, or they double the total EXP.