Safe working load limit is more precise but the concept is the same. The 2000 lb breaking point has been derated by a factor of 4 to give you a "safe" capacity of 500 lbs.

What I have yet to figure out is if I could lift an 80 pound sack of cement with just a line in my hand. If I can, then a 7:1 would exceed the swl but still come nowhere near the breaking strength.