The Feecof test assesses your setup's ability to render and process rich WebGL content. It is mainly made for TETR.IO, where it runs on first launch, and is used to decide on a graphics level to initialize to.
It is not particularly accurate, so it is by no means a benchmark of any particular setup. After all, it is only made to give a vague indication of how well the setup will perform in an abstract situation.
In general, the average Feecof score is 500,000. The score depends on both the hardware used, as well as the browser running the test. In general, TETR.IO Desktop (which is an optimized Electron/Chromium instance) will provide the highest scores. Chromium-like browsers tend to score similarly, while Firefox-based browsers tend to score rather poorly. These results translate into real-world (TETR.IO) performance as well, where Firefox-based browsers indeed perform poorly compared to Chrome-based browsers.
The Feecof score is interpreted by TETR.IO to decide on a graphics level on first start. Scores under 300k default to "LOW" graphics, scores between 300k and 600k default to "MEDIUM", and scores above 600k default to "HIGH". If the player is running TETR.IO Desktop and their setup reaches beyond 1m feecof, then "ULTRA" will be selected.
Did you know: On average, the ingame version of the Feecof test renders about one million Kagari sprites (the one you can see in the logo) per test, and takes about three seconds to finish (the ingame version is shortened drastically to prefer speed). As of the time of writing (2021/11/05), 2.7 million such tests have been run. Hence, about 2.7 trillion Kagaris have been rendered, using a little under three months of processing time! Sadly, this doesn't make her any more real.