Im sorry this can be tricky when youre new, but we got you and we're patient. 
Do 8.2 to 7.8. Its at 8.6 in your poolmath.
Lower the Ph by 0.4 at a time. When it's a mid 7, calculate that last bit in poolmath to make it a low 7.
Do 8.2 to 7.8. Its at 8.6 in your poolmath.
Lower the Ph by 0.4 at a time. When it's a mid 7, calculate that last bit in poolmath to make it a low 7.