Hi Newbien, backspace is 115mm remember Rear Wheel Drive.
Thats from the back of the inner flange to the inner lip - thats the clearance they're not stamped with the offset
but, 7inch = 176mm divide by 2 = 88mm less 115mm = 27 offset
give or take a couple of millemetres.
I think that how you work it out but, don't take my word OK.
These are NOT the 5.5inch or the 6.0inch or the 6.5inch width - they are definite 7.00JJ width.