If I plug your info into hamz reef, this is even what it says to do
FYI: You can find this calculator and many other helpful ones at :
Target Salinity Calculator
Aquarium calculator; Create a water-change schedule that can be used to reach a target salinity.www.hamzasreef.com
There is probably a clever reason it wants me to use larger quantities of mixed salt rather than smaller quantities of RO/DI but I'm not seeing it... I doubt I even have enough salt for that proposal! I see a lot of water changes in my future.