$40 Tip on $500

We went out to dinner as a group and the bill came out to $500. We left a $40 tip, feeling good that we were still able to give something, but the server didn’t seem happy at all. She actually said she was expecting at least $120.
When we asked to speak to the manager, she quickly tried to brush it off and said she was joking, but there was no smile or anything to suggest that.
Now I’m just wondering if $40 on a $500 bill is considered enough. Expecting $120 feels a bit unrealistic to me, but maybe I’m missing something