MMQ and 15 days

I am, among other things, the MMQ nurse for my facility. We just had our turnaround. I claimed a skilled procedure because the gentleman had a treatment which,although had many changes, was done for more than 25 days. The surveyor disallowed the points because she didn't count 15 days. I have no corporate support and am, obviously, clueless about this, but I thought I could claim a skilled treatment if it was done for 15 days or more. Anyone know????