As a general statement, the test strips for salt are probably not that reliable. And for what it's worth, the little battery powered testers used by the pool stores also vary. I would also ponder a guess that if your salt level is too high OR too low, the system will in all probability still work, just not as efficiently.

I treat my SWCG kinda like my spouse, she is the only one that I have to satisfy. In other words, as long as the SWCG is producing chlorine and working well, and the high salt and low salt lights are not coming on, you're Golden.