>>508404760There are more than 10 commandments when you look in the Bible, Protestant or Catholic. It's just how you group them. Why they're call the 10 commandments, I don't know. Really there's 12 of them in total if you really want to break them down.
Catholics group the first two because they pertain to the same sin, idolatry. And they split the last two because one pertains to lust/envy and the other just envy. And of course, Protestants do the opposite, hence the difference.