I have posted in the past asking exactly what the RG and Differential do for a ball.

This time I am curious about a couple of things. First being MB differential. Can anyone explain what this means please?
I have an idea, but I am not sure.

Also, I remember reading in a post one time about how to find out where you really are on a bowling ball is to subtract the differential from the RG and that gives a more accurate idea. Is this true, or is there something like this and I am actually just saying it incorrectly? Can you please elaborate on this a little for me as well?

Thanks very much! I am going to a week long drilling seminar in 2 weeks and want to try to have an idea of what most numbers mean to a ball.