QR plate question

Am buying new tripod for 7D + Sigma 120-400 OS + flash as my heaviest load. Have decided on manfrotto 055CXPRO3 legs + MH054MO ball head. Problem is the head comes with different plates, & I am not sure what the No's mean. There is Q2 + Q5 & I think one or two more with different Q No's. Could someone explain what is the difference? Hope you can help.

--
lee uk.
There are old pilots, & there are bold pilots, but there are no old bold pilots.