Of what importance is it? All the fuel
the engine doesn't need goes back.
As long as you valving system ensures that the overflow goes back to the same tank it came from, no problem. Some systems (mine is one of them) has two valves and if forgetful it is possible to return fuel
to another tank and that's not clever, especially if that tank is already full.
If you have a smaller volume "day tank", use it always because returning fuel
to a tank where it will live for a while will lift the temperature of that tank and promote condensation and the growth of bugs and other uninvited guests.