Defending against damage seems to contradict itself. Page 268 says in bold; "To defend, they must receive an amount of fatigue equal to the remaining damage;" then goes on the say "otherwise, they suffer a critical strike with severity based on the source.
But then on the sidebar next to it "a character can still defend if if defending would cause their fatigue to exceed their endurance."
So the example I'll use is; you're hit for 7. Your armor soaks 2 of it to 5. You need to suffer 5 fatigue, but are at 6/10 endurance.
The first case seems to suggest rather than suffer fatigue, you suffer a crit as you can't defend. You remain at 6/10 and roll fitness vs their crit.
The second case seems to say you go to 11/10 and are incapacitated.
Any help here?