Comp has done away with the lifter rebuild program.

Spring “rate” refers to the change in load over distance....... usually lbs/in.

So, 545 would mean a change of 545lbs in one inch.
If you know the load with the valve closed, and the net max lift at the valve, you can calculate the theoretical open load.

Example, 220 closed and .685 lift.
545 x.685 = 373.3, add in the 220 = 593.3 open load.