Sorry, but you asked for a sanity check, but appear to have gotten an insanity instead. 10 cm = 1 meter. Square both sides and yes it is a 100:1 ratio. Your area is 100 times larger. If your contamination was uniformly distributed, you would have 100 times more contamination. But why would anybody want to know this? How are you measuring it? What is your sample area? How many sample areas are you measuring? How much pressure are you applying to the smear? Is the contamination uniformly distributed? What is/are the nuclides? What detection instrument are you using? Is this a scientific experiment where you are applying contamination? Oops, I digress, you asked for sanity, and I gave you insanity instead.