How deep it should be placed?

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Today I drove into petrol station in city. I opened my car fuel tank cap and put fuel hose into it. Diesel began to flow into the tank. I released hose handle and waited until when my tank will be full it automatically stops the fuel pump. But this time it stopped faster than usually. I tried to puor more fuel into tamnk manualy and succeed with some 15litres more. So now i am thinking how deep i must put fuel hose into my fuel tank opening to get as much fuel loaded as it is possible and so that fuel dont start to fizz so fast.