I'm buying the minimum, 500.
If you took the trade by choosing the amount based on a range, what you see might be a bug and could be considering the minimum value of the range, although when the trade is executed, you will receive what you are entitled to.
What do you think nostr:npub1v3tgrwwsv7c6xckyhm5dmluc05jxd4yeqhpxew87chn0kua0tjzqc6yvjh?
Discussion
It's a bug. Tha happened before but you will receive the correct amount.
You can try robosats app and you will see everything is right.