Hmm thats definately not the recomended BBS fitment. did your wheels have the antislip coating on the inside where the tire seats?
It should be the same spec as the GTR actually
20x10.5 +20
20x9.5 +40
GT Motoring is an authorized BBS distributor, so if you guys have any questions on fitment, feel free to hit us up. We have these LMs in silve and gunmetal too! LOVED them on my R35 GTR