I'm using the Taylor salt test kit. On the 24th of June I tested and it was at 3,000 I tested again on the 29th and got the same result so I added a 40lb. bag which according to Poolmath would have brought me to ~3,200 ppm which is where I wanted to be. Today I tested and I'm at 2,800. I'm not sure how this could have happened. We had a little bit of rain, but I don't think it's anything that could have impacted the numbers by even close to that much. Is there anything else that could cause a 'loss of salt' aside from water replacement? My test kit is about a year old if that matters.
Also, just to be sure I'm doing it right:
10ml pool water
one drop yellow
drop of brown until water turns 'salmon color'
multiply by 200