"negative" page numbers?

I had a PTXPrint job where I had a PDF file of cover, blank back of cover, title and credit pages that I included as a front matter PDF, and PTXPrint counted all of those pages when it was deciding what page numbers to use for the text. So in other words, it counted the cover and the blank back of cover as pages 1 and 2, the title and credits pages as 3 and 4, so it started the text on page 5. Counting the cover and back of cover is not what you would want. But the only place I found to adjust that was the Starting Page Number on the Header + Footer tab, and it would only allow the number to go as low as 1. If I have cover and back of cover in the front matter PDF, I would like to set that number to -1, but that isn’t allowed. Should it be allowed to let it be a negative number?