Please stop cross-posting about the same issues in the forums and the issue tracker.
It doesn't have anything to do with hexadecimal, rather with the fact that OpenMPT starts counting at 0 for everything, yes, even for samples and instruments, where "0" means "no sample / instrument". If someone tells you that's not logical, then ask them why they start counting at 1 and not 0. You can also count your beats starting from 0, if this is something that wouldn't cross a classically trained person's mind then it's not my problem.