Robert,
There is a whole thread on blade sizing for SawStop.
In short...some 10" blades were manufactured to metric sizes and actually measure out at roughly 9 3/4" instead of 10. In my case they were Freud blades. I understand new ones now are full 10".
This didn't matter until SS became popular, and they are made for 10" blades, although should adjust to the metric sizes also. Again, in my case, I did not want to adjust with each blade change, and only use full 10" on my SS, using the old ones on another saw.
Hope this helps.
Rick Potter
DIY journeyman,
FWW wannabe.
AKA Village Idiot.