The first rule would have index 0...

I expect the third to be 10

This is underground programming. Perhaps it's 1?

I'd make it -1, that way regular programmers wouldn't know about it.

"Should array indices start at 0 or 1? My compromise of 0.5 was rejected without, I thought, proper consideration." — Stan Kelly-Bootle.

I'd say that's the zeroth rule.