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What's the difference between Frame Rate and Refresh Rate?
Frame rate is how many frames per second your game is running at, refresh rate is how many times per second your monitor refreshes. So 60fps at 60hz means you’re running and seeing 60fps properly.
If your screen is at 30hz, and your game is running at 60fps, you’re only seeing 30fps.
Try to keep them matched up for a better experience.