There is a "dry" gallon which was a portion of a bushel in old commerce. A dry gallon converts to 6.48 dry gal to the cubic foot and (of course) we have the IMPERIAL gallon which is 6.28 gal to the cubic foot.
You may be right depending on which measurement standrd you were using.
REally, nobody uses the dry gallon any more cause the W bushel is an archaic measure instituted by King Alfred (he was a king of England before many of us were born)
Alfred said, in his desire to unify weights and measures, the following:
8. & gange án mynet ofer ealne þæs cyniges anweald, & þone nan man ne forsace.
§1. & gange án gemet & an gewihte, swilce man on Lundenbirig & Wintaceastre healde.
§2. & ga seo wæge wulle to cxx p', & nan man hig undeoror ne sille.
chapter 8. And let one money pass throughout the king's realm; and that let no man refuse.
§1. and let one measure and one weight pass; such as is in use in London and Winchester;
§2. and let the wey of wool go for 120 pence, and no one sell it for less