That additional info would be necessary to submit a suitable image.  Am I not correct?

Bingo! More often than not, I just wish they (Rendo, clients, etc.) just gave you the pixel dimensions they want and skip the dpi altogether. the dpi is the 3rd part of a 3-part equation, and it means the least. Kinda frustrating.

20in x 20in would be 6000 x 6000 ppi/dpi...right?

Yep - exactly!

-Lew ;-)