If you are an on-site guest, you can call 180 days from the start of your hotel reservation and make 10 days worth of reservations at once, hence 180+10.
If you stay off-site, you can only call 180 days out from the date of EACH day that you want a reservation for. So if you wanted 10 days worth of reservations, you would have to call 10 different times (or wait until the last date and make them all on that phone call).