Just as I suspected, putting in an "a" would make all the difference.

Yes but I shouldn't need to word something perfectly right to get an answer that's not the exact opposite of what I need.
Honestly my first search was "oz in gallon", then I tried this just to give it another chance...
Chat GPT and even Gemini had no problem knowing exactly what I needed:

For the haters of AI results in google this is a case where I (would) love it. Obviously I hate that this is all built on my simple inability to remember basic grade-school math... but whatever