Is there an official documentation of what "Render Nom" and "Total Render" mean in the shift f1 overlay?

a few days ago it seemed to be sort of linked to my fps, if i was playing a demanding game and my fps was averaging around lets say 120 fps, my render nom would be around 120/s however this doesnt seem to be the case anymore, as my render nom is usually a bit higher, and in the past, ive never seen it go above 1000/s but now it easily does in baseplates.

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