Keys are available in 4 offsets:

0.7mm [621 991 04 67] 4deg. crank
0.9mm [621 991 02 67] 6.5 deg.
1.1mm [621 991 01 67] 8deg.
1.3mm [621 991 00 67] 10deg.

Choose 6.5deg; chain and sprocket wear will negate the 1/2 deg. difference.