I played so long with the bromine levels that finally I gave up and took the Chas rule of new tub owners, and dumped the water! Your tub is new so you are not even close to that yet.
Hopefully I can explain things and if I mess up, someone will correct me.
The Frog system injects bromine every time that the #1 pump runs (unless of course the cartridge is closed completely). So your filtration cycles, and the number of times that you turn on the tub (Remember every time you turn on the tub jets to show someone, or to just look at how nice that baby looks on your deck..[.I used to just turn it on to look at the waterfall]... will trigger a smart clean cycle, because the tub thinks you have just used it. What I am saying is you may be running the tub a lot and injecting bromine but since no physical bodies are in the tub using the bromine, the level just continues to increase. When you introduce "bodies" into the tub, the bromine goes to work grabbing up all the organic material (bacteria etc). So your bromine levels appear to drop. I say appear because when you shock the tub, you oxodize the organic material and free up some of the bromine to work again. Now you have recycled bromine AND you are injecting bromine. The balance will happen when you establish some sort of routine for bather load, so you know when to shock. I would just say again, since you have turned your frog cartridge completely off...you need to watch that bromine level and when it appears low, shock...wait a while, test again and at that point you may need to open that cartridge back up to about 2. Hopefully this helps and if I have made any mistakes, someone please correct me :-/