The the visible gas pump gallon measuring number placement up or down, depends on the dispensing system used - wet hose or dry hose.
Many early visible pumps were set up with a dry hose with no valve on the nozzle. The amount of gas requested was pumped up into the cylinder, measured from bottom up and then a valve at the cylinder was opened and that amount of gas was delivered to the car. At the end of the transaction, the cylinder and hose were dry.
On the wet hose system, the cylinder would be pumped full and the hose nozzle would have a trigger shut-off valve. The amount of gas delivered was measured from top down in the cylinder. The hose would start full of gas and end full of gas, the way gasoline is sold and dispensed today. Visible gas pumps that started out as dry hose were often converted to wet hose later.
Numbers counting from top down are wet hose delivery and from the bottom counting up are for the dry hose.
This doesn't include variations that included ways to bleed off or otherwise cheat the customer out of a portion of the gas that appeared to be delivered.