I think you might be reading it wrong. The way I read it is 17% of those with two to five preparers use Drake tax. That does not include firms with only one preparer. 30% of firms with only one preparer used Drake tax. 44% of firms with 501 or more employees use CCH access tax, and that makes sense as it caters to large firms. The 44% does not include firms with one preparer,  or two to five preparers, Etc, it only includes those with 501 or more. Hopefully this will clarify this, but who knows, sometimes I do spreadsheets from right to left.