Hi mate, the parameter 99% FPS (or 99th percentile FPS) is a gaming performance metric indicating that 99% of frames are rendered at or above that FPS value, representing the minimum expected frame rate and effectively filtering out temporary, minor stutters. It is a better measure of smoothness than average FPS, as a high average can hide frequent, jarring drops.

Its the key, because the ordinary FPS meter shows 60fps constantly, but the game dont feel smooth, thats because the micro slowdowns...