Making Phosphate Buffer Calculator How To Make 20mM Disodium Phophate Buffer (pH=7), Excluding Monosodium Phosphate.?

How to make 20mM disodium phophate buffer (pH=7), excluding monosodium phosphate.? - making phosphate buffer calculator

I found the results but with all of monosodium phosphate. I'm only 20 mM disodium phosphate buffer to make, go no MSG.