180 + 10 means that you can make all your ADR's on the 180 day mark of your trip a a trip that is 10 days or less. If you are staying longer than 10 days, you have to wait for the 180 days of day 11 of the trip.)
180 plus 10 was put into place so you don't have to call every day to make a reservation 180 days out.
It doesn't mean that you call at 170 days.
Keep in mind that just because you call at 7a on your 180 day doesn't guarantee that you will get b-fast at CRT for your exact time and date. Remember that date already fell into place for other people for their 180 plus 10.
I'm re-reading this and it sounds soo confusing.