I don't understand the Paint Shop Pro general preferences, Units, Defalt Resolution, set up.

I was told in my online PSP class to set it at 78.780 pixels per cm, but I have no clue why nor what this means, and the only answer I can extract from the course leaders is a vague statement that Corel said to set it that way.

I cannot find where Corel said to set it that way, nor where Corel or anyone else says a word about it. I can't find it in Help, in the user manual, nor through Google.

What does that set of numbers mean, and how do I really decide what setting to give it?

Thanks!

Yours,
Dora Smith