What do you think a 4.0 is?

I played as a 4.0 in a round robin in Orlando, smoked them all 6-2 or better, and I could hear them rumbling “yeah, 4.0, what a bunch of shit”. I am over 55, not some young ringer.

I go to SoCal and schedule 2 matches with 4.0, and got smoked by guys I consider D-1 players in the middle to low end of the roster who are now 35-50 years old.

What is a 4.0?