KZ Reefers best salt alk 11

[Roskoreef]

Im getting ****ed off now.

Reefers Best Salt 99$+ these days, 160 Gallon yeild for what?

This salt is supposed to be Alk 7, first 3 boxes were pretty close , 7.7 at the highest. Last 2 boxes, Alk 11! WTF. I run my alk at 7-7.5 with zeo so..

Help, how does one:

a) Lower Alk of NSW
b) Do water changes with an alk difference of 4

I have alot of fish, i rely on weekly water changes to keep my phosphate and nitrate down to keep my sps as happy as can be..

stumped...