Pointer wrote:

And check your "gallon" carefully and you might find it is not a gallon
anymore!!! As is the case with ice cream, pound cans of tomatoes, etc.

Not exactly. Truth in labeling laws require that manufacturers show the exact
volume of paint containers. If you buy a "gallon" of paint that can be used as a
tint base, it will likely be less than a gallon on the label.