For bumper is it 8" of bumper or 8’’ of frame covered by bumper?
This forum has a great search feature. If you search “bumpers” or “bumper rules” you will find a number of threads asking this question or giving you answers from the manual or the Q&A.
I second O’Sancheski’s point. To answer your question, your bumpers must cover 8" on each external vertice (not sure if I spelled that right) of your robot.
Robots are required to use Bumpers to protect all exterior vertices of the Frame Perimeter. For adequate protection, at least 8 in. of Bumper must be placed on each side of each exterior vertex (see Figure 4‑1, Figure 4‑2, and Figure 4‑3).
Since the exterior vertex is the corner of the frame, that means 8" of frame, not bumper