If you have LR and LS there is no point whatsoever in adding a bottle of stuff that sits on a shelf, seriously.
The bacteria you are adding is like the bacteria on LR (that is, if it is still alive after sitting on the shelf). If you have an established tank an 0 ammonia levels, then you have enough bacteria to utilize the ammonia in the system produced by critters. Adding more will do nothing. They need ammonia to live, basically, and if there is not enough they just die off. The lifecycle of bacteria is extremely rapid, so the bacteria in your tank have a head start. Yes, you can still get ammonia spikes and it may take a few days for the bacteria to reach concentrations where they can manage it (assuming this is not a tank "crash"). But, IMO, adding cycle to an established tank will do nothing and is a waste of good money. I would always suggest spending that money on more LR or better foods, etc.