The Standard account hosting package is 2 accounts regardless of whether its a master or slave to a copier. With this package you can create 1 copier with 1 master and 1 slave account.
It works the same way for each account hosting package. If you upgrade had the Plus account package, you could have 1 copier with 1 master and 4 slaves or 2 copiers with 2 masters and 3 slaves. The account purpose doesn't matter.