The output is only showing you have 5 extension boards so the output is correct, 8*(nbrd+1). That’s 48 stations so 6 sbits is correct. If you actually have 6 extension boards attached one of them is not being read and is possibly a hardware issue.
I looked through the firmware and I don’t see anything that would cause the output to be incorrect software-wise.
Are you using official Opensprinkler hardware? I know sellers on Amazon have one, and if that is what you are using you may need to add a series resistor to their board to make sure it is detected properly.
****EDIT Okay never mind on that idea, the OSPi doesn’t use the detect function. So I would try renaming nvm.dat to something else and then rebooting again. It should recreate the file, and then you can check the board count again. If that changes I know where the problem is, if not I’m at a loss and would probably have to defer you back to Ray.