Replying to Rossignol Create It Question (Concerning Photoshop)

The directions ask for 3000 dpi for Photoshop. Does that mean if I'm scanning images in, all images must be scalled to 3000 dpi? This could mean for the largest and most intense file I've ever tried to process.. I want to do some collaging with images and such, so I'd like to stick with PS. But if its at 3000dpi, the file would then correctly have to be at full size? So it'd be a 6 foot tall by 8-12 inch wide canvas at 3000 dpi.
So basically when you viewed the photoshop file, it would give you a preview of everything at less than 1%. It just seems absurb to me and I wanted to make sure I'm all correct on this..and that everyone else is working on 3000dpi in Photoshop also. And if so, whats your canvas size at?