You have GOT to be kidding!
In a self-serve station, I don't have to wait for the attendant to come to the door, nor do I have to wait for the attendant to receive payment. I just insert the card into the pump, pay, and pump. Not exactly a highly-skilled technical job!
Honest Injun. You want the highest pumped volume you go attended. And then figure about 100 seconds per tankful per attendant. Mabe 120, to give the boys a rest.