A pool with a SWG is still considered a "fresh water" pool, having a salt level of about 3,200 to 3,800 ppm of salt. This is the salt required for the system to generate chlorine properly. This is approximately .32% - .38%

A true "salt water" pool has sea water or water with salt (and other mineral) concentrations about 10 times higher, in the range of 3.1% - 3.5%.

It takes special equipment to handle a true "salt water" pool. Your FNS should be fine.

20 years in the business and still learning.