[MD Longhorn]

I believe the quiz is for NCAA, but comment on the rulings in both:

PLAY: 4th and 9 on B's 41. B23 muffs A8's scrimmage kick on B's 7 and the ball rolls into B's end zone. B23 picks up the ball and starts to run but fumbles the ball while still in B's end zone. B56 recovers on B's 2 and advances to B's 22 where he is downed. During B23's fumble, B55 blocked A74 below the waist on B's 6.

The stated result in the quiz is:
RULING: Safety. B's ball, free kick, on B's 20. B55's foul occurred during a running play that included B23's run. The end of B23's run was in B's end zone. Acceptance of the penalty results in a safety regardless of the spot of B55's foul. If B23 was tackled in B's end zone (no fumble), then the basic enforcement spot would be B's 20 and the 15-yard penalty would be enforced from the spot of the foul, B's 6.

This feels wrong to me. Isn't it B's ball on the 10?