Where can you tell that it lets you turn in the level 20 leve three times as one allowance??

Honestly I have a lot of leves saved up because I haven't needed to really use them to level anything but miner and grand company stuff. He showed a full screen of that leve information and it doesn't say anywhere on there that you can turn those 5 pieces of leather in 3 times on the same leve. Is there any way to know from reading the description?

In regards to his real question, about why the reward is higher for the level 15 quest, I think it's because in the level 20 quest you give your leather to Maisenta. She is located right in Gridania, less than a full sprint away from where you most likely accepted that levequest. The level 15 one is turned in to an NPC located in a different town in the Shroud. I think they compensate you better for having to travel. That's what I've noticed anyway.