Check your manufacturer's recommendation for the salt level that you need. Usually, SWG pools need a residual salt level of 3000 ppm, give or take, but this can vary according to the manufacturer.
Looks like your pool is 8200 gallons. With your beginning salt level of 470 ppm, Jason's Pool Calculator results that you would need to add 212 pounds of salt to get to 3000 ppm. Looks like you have probably gotten close to that by adding those 4 50 lb. bags. I would wait for all of the salt to dissolve and check the level again.
You might like to bookmark Jason's Pool Calculator for future reference. It really is a great tool to have at your disposal. You can find it here: http://www.poolcalculator.com/