Order count not matching single sale order report

I feel like I may have asked this before, but I have a widget that gives me a total count of web orders for a given timeframe. In the past, I thought this had matched the Single Sale Order report for the same time frame, but this quarter it is off by nearly 200. 

My formula for # of unique order ids is count([Order ID]). 

My date filter is at the dashboard level. I tried turning it off and adding one at the widget level, but that didn't make a difference. My question is -- which is correct? And can anyone explain why they don't match?

Thanks! 

Anne