When to use seafoam treatment in the gas tank

[TMMK Toy]

Bought some Seafoam while at autozone getting my oil and filter. Just wondering if I should add the contents before or after I fill up and if the contents of the whole can should be used? 1 pt (a can) treats up to 25 gallons of gas, so didnt know if I should use that much or less since my tank holds more around 17 or so.

[Ruski]

whole can to a full tank of gas.. i have never noticed any diff from using it in the tank. i always do braker booster. and a lil in the oil. Read my thread on Sea Foam