Yossarian wrote:

I understand that functional fuel gauges are required equipment for day VFR
flight.

Per the FARs, your gauges were functional. The only requirement is that
when the tanks are empty, the gauges read empty. If they show full when
the tanks are 1/4 full, that is not a problem in so far as the FARs are
concerned. Repeating, the only regulatory requirement is for gauges to
be accurate when the tanks are empty. That's why you should pay little
attention to them at all, and do your fuel calculations with diligence.
-angus