Oh, for goodness sake! How painful can this simple question get?
If you get fewer than 30 Reserve days or 30 A days, then both are "free". For most people, on most bases, that would hold true.
An A day at the start of a pattern does not add to the "1 off in 7" requirement, but an R day does. Whether this affects you or not depends on the average length of your pattern. If your patterns routinely have 30 hours off duty somewhere, then again this becomes a moot point.
On an A day you only have to be contactable for 8 hours, and then - and this is very important - you don't have to take the offered duty if it starts in less than 10 hours. On Reserve, you are by the phone for 12 hours and HAVE to be at work within 2 1/4 (or is it 2 1/2?) hours.
You must contact CC on the day before the A day (between 1200 and 1400 local base time) to see if they have a duty for you for the following day. If you had a reserve instead, then the first you would know about your new duty would be a phone call at 0600. Either way, they can get you to fly the next day, the only issue being the amount of notice.