The instruction manual for your grinder should show you how to center the chain holding vise to get equal length cutters.
This setting can change as the
grinder wheel wears and the diameter changes.
Or, you can adjust your technique: I will grind all of the Left cutters (for example), then do just one Right cutter. I stop and compare that cutter back-to-back with one of the Left cutters, and make small adjustments to the cutter positioning stop / dog to get equal length cutters.
After a while, you will be able to predict which side will be longer without making the adjustment.
Philbert