Guild Wars 2

Every time I try to limit my frame rate to 30fps, I always get a result a 20 fps. I have no idea what happened.
If without any limitation, my framework should be around 50-60fps, so it’s definitely not because of my computer’s low performance.

With such a vague description of the problem (lack of computer specs, general software in use, operating system and in game settings,) I’ll have to go with potato for lack of a better answer to your problem.