Well i just started out a cafepress shop and im trying to make a plain white t shirt. Right now im working on the logo, and nothing is just working right. They say "Image Size: 8 x 10 or 10"

so i asummed that was in inches, but when i did it in inches it just came out to be a blob of nothing on the shirt. Now i dont know what to do. Can anyone help me please? Thanks