How to tell brake proportioning?

I have a question about my rear brakes, I stood the rear up on stands and got them spinning and hit the brakes to see if they immediately stopped... and they did. Only thing is my left rear doesnt leave nearly as much dust as the right rear and they have the same pads and everything on them, just wondering if the amount of brake duset left is proportionate to the amount of braking its doing...?

Compare the pad thickness from the left side to the right; if the thickness is equal, you're fine. There's not a proportioning valve from left to right, just front to back. If you have uneven wear from left to right, your caliper(s) need to be rebuilt or replaced (one's "hanging up").

just what I needed to know, thanks man.