Confused about PPI inb GIMP

[vixko]

Hi, I've just started to use GIMP. I scanned in an image at 1200 DPI. The document is 6 x 8.5 inches but when I open the document in GIMP the "set to canvas size" shows the size to be double but 300 ppi so I'm confused about the sizing. Another image/document I scanned in at 600 dpi is the correct size on GIMP (6 x 8.5 inc) but the dpi is 300 - surely it should be 600 dpi or double the size? Can someone please explain this to me? Am I looking at the wrong place to find the size of my document? I need to generate digital prints at the largest size possible at 300 dpi. I'm on a MAC. Thank you