Calcuim high without ever adding any?

I have been buying the 5 gallon bottles of culligan ro water, I dont know if it is the best, but I have no algae but the pretty purples and everything seems to like it. I decided not to go with an ro unit at this time, still trying to find a whole house system and the culligan water is woking out great for me @ $4 a bottle.
Also, some lfs sell ro/di premixed, mine is 1.024 sg @ 65cents a gallon, I dont want to trust her water yet tho cuz she just set it up a few months back plus she is about70 miles down the road. I guess that would make her an fs instead of an lfs then huh?