4 to 400% is an awfully big range!
I have mixed thoughts about bottled bacteria to begin with. When I opened my store, I had over 70 tanks/racks to cycle and used filter squeezed water on a few, used several major brands of bottled stuff like Cycle, as well as control tanks that got no BB. Some even got the fancy glass vials of BB but I forget the brands now. In the end, there was no rhyme or reason to which tanks cycled faster fishless, though to my recollection the two fastest were seeded with filter water. This was 2007 though, and I've seen evidence to believe that they've come a long way since. In my recent shrimp rack and the ADA was spiking ammonia well over 5 PPM in two tanks. I used the newer Tetra Safe Start product and to my surprise the NH4 reading was .5 in less than 48 hours. But my question about the Tetra product is, what are the contents of that bottle? Is it truly only bacteria in suspended animation? They surely couldn't survive on a warehouse and then store shelf for months or a year in a sealed container with no food or oxygen, could they? Does the product contain anything else that could bind or chemically remove ammonia? Nothing to suggest that on the ingredient panel.
Nothing good happens fast in an ecosystem.