wait! salinity between 1.020 and 1.026 is a HUGE range....
what are you using to measure your SG?
stay at 1.025 OR 1.026. pick ONE, You want to figure out how much salt it takes (literally take a scale and weigh it) to make ONE GALLON of RODI into 1.025 saltwater. For me personally it is 143grams of Fritz RPM salt blue bucket to get 1 gal @1.025. this way every time I mix water, i just weigh 143g of salt, fill 1 gal and just never worry about it. I only measure my salt when i get a new bucket, I make a 1 gal batch of that new salt and measure it all, then i know exactly what that bucket is. A bucket lasts me about a year. Hope that helps.