User blog comment:MachineGunSuper/Millillionbulls/@comment-80.98.179.160-20171221193239/@comment-30754445-20171221195719

It could also simply mean an exclamation mark, rather than a factorial.

Doesn't really matter, though. The size of the number is chiefly governed by the number of arrows (which I'm too lazy to count) and a factorial won't have any effect on that.

In my Psi Levels scale it would be a low class 10 either way (class 10 goes from 10 to 1010 arrows).