Just random numbers I think?
Presumably avoiding divide by 6 so you cant use a torx/triple square and hammer so easily?
SB0 / 10 point
SB1 / 11 point
SB2 / 13 point
SB3 / 14 point
SB4 / 15 point
SB5 / 16 point
SB6 / 17 point
SB7 / 19 point
SB8 / 20 point
SB9 / 21 point