When I used to dose phosphate, I went with Randy's formula:
1. add 1.88g of Trisodium Phosphate to 1 liter of RO/DI
2. adding 1 mL per 100 L of tank water will boost phosphate by 0.01 ppm
...for my roughly 32 gallon volume, that seemed to work out to 5 mL solution dosed boosted PO4 by about 0.04 ppm
*scale that to 220 gallons and 34 mL dose of the mixed solution "should" raise PO4 by same 0.04 ppm,,, so from .07 to .11 ... but, I'd start with smaller doses and test.
Since you're dosing, you likely have significant uptank/binding so you just have to dial in your daily dose based on testing anyway.