Problem with changing size of text

I am having a problem with cutting the size of text that I want. On the main working screen I type in the specific dimensions of the text that I want to cut ( I have a graphtec cutter). When I pull up "Cut/Plot" in the dialog box under Job Size....the size is NEVER what I have specified. It is normally smaller.
I will then type the dimensions into the Job Size field and cut the letter. BUT when I cut the letter......it is not the size I typed into the job size.

I really need help on this! I'm very frustrated.