That’s not a glitch. The amount of bells you receive depends on the length of your post and the board it’s posted in. When you edit, you may delete or add things which can change the amount of bells you recieve. Therefore, when you save your post, it either keeps it the same or changes depending on what you delete from/add to your post.
Also, I don’t believe there is a limit on the amount of bells you can earn per day. The most bells I have ever received from a single post was 15, from the “What are you happy about today” thread. I’m assuming that’s the cap, and you can’t earn more than that. (I mean, aside from bell bonuses like Leif is doing right now.)