Doug,
If I recall correctly you have to look at the bond order for both sides of an ij pair. You have to look at ijk where k is bonded to j and jil where l is bonded to i. Add the two and then divide by two to get the average bond order for the pair. See equation 3 in Brenner 2002.
This off the top of my head with out digging into the code. Hope it helps.
Dave