A couple of weeks ago I was able to book 11 days worth of ADRs when my 180 day window opened. This included dinner on the 11th night.
I initially tried to make ADrs using the new WDW website but it would only recognise my arrival day. So I gave up and rang instead and got everything I wanted. I can't speak highly enough of the service I received on the phone. However the woman on the phone did seem as surprised as me that I was able to make bookings for the 11th day (I'm not sure even Disney employees are 100% certain about how the 180 + 10 is calculated).
Also, a side-note incase it helps anyone, those 11 days covered a split stay under 2 different reservation numbers (i.e. 5 nights at BWV, followed by 6 nights at AKV). I was worried that I'd only be able to book 5 nights worth of ADR's to start, so asked here on the DIS about whether split stays affected the +10. It was another area of ADRs that people were unsure about and I got some very contradictory answers. It seems, however, that split stays do NOT affect the + 10.
Lastly, when I called at 180 days to make my ADRs, I also made enquiries about Pirates League for the second day of my vacation. I was fully expecting to have to call back the next day to make this booking, but the dining reservations woman booked it for me then and there. It was almost as if the Pirates League was being treated as a 'plus ten' just like the dining. I'm not sure if this is always the case, or I was just receiving some pixie dust, but I thought it was worth mentioning incase it helps someone else.