My guess is that because the gasoline was pumped in slowly, there was less backpressure to trigger the shutoff on the nozzle. Therefore you probably filled the tank and the filler tube. All states have a bureau of weights and measures and pumps are checked for accuracy.
Here in Indiana we had a chain store that is no longer in business called Quality Farm and Fleet. In the house brand motor oil called Harvest King, the bureau of weights and measures discovered that a quart of oil was about 1% short and all the oil that hadn’t been sold was pulled from the shelves. Customers could return the oil that had been sold for a refund. I didn’t bother since I didn’t think it would make that much difference to me. Apparently it was not a deliberate mistake to bilk the public–something had gone wrong where the oil was put in bottles.