FPS predictions are based on average gaming sessions, on (preset) highest settings. These differ from those some users may experience using custom settings.
Our FPS Guarantee is measured over the course of an hour-long session, when we refer to the highest "preset" setting, this would be a pre-named graphics setting like "Epic" or "Ultra". We do not enable any visual enhancing effects such as anti-aliasing, RTX Shading, or resolution hyper scaling. Like in Fortnite shown in the photo below has "Epic" settings.
We guarantee the framerate within 10% of the number we state on our site, if you ever have an issue with your framerates you can always contact our service team for assistance.