what does this refer to as it doesn't match big ring front big ring back. cheers

Total capacity is worked out by adding the difference between big and small chainring to the difference between big and small cassette sprocket.

(44-22)+(32-11)=43

it's basically the difference between the big-big gear and the small-small gear (although there are other ways of phrasing but the answers are exactly the same)

eg. (on a roadie)

big-big could be 53 and 25

small-small 39 and 12

difference is (53+25) – (39+12) = 78 – 51 = 27

obviously longer cage mechs have a bigger capacity

Mister P has described the other way of phrasing it 8)

but they get the same answer

thanks people