The way you calculate FC added is by the following formula:
(1,000,000/PV)*Conc*Amt= FC

PV= Pool Volume
Conc= Concentration of bleach as a decimal, so 6% is .06, 8.25% is .0825
Amt= Amount of bleach added in gallons--I usually use 1

To convert to odd amounts set Amt to 1, then divide by 128 (ounces), then multiply by the odd number of ounces.