Oil level in auto box

hello changed to auto fluid in my box because a mobile mechanic put red dexron in it when it was my daughters car,instead of the yellow peugeot it has no dip stick ,it has the over flow system in the sump drained the box and got 4 1/2 lts off,but I can only get 2 back into it before it comes over the over flow tube ???,I filled the box using a tube and pushing it down into the box (about 7 inch )took it for a run to warm up and took out the 19ml overflow stud and it just dripped out telling me its spot on ??? but how can it be.the book says it takes 4 1/2 lts from draining,the box holds the other 2 and can only be taken out by taking the gearbox off (the book says )its flashing the snow and ice the will have to be re set by peugeot,but no point if the level is not right and they want £50 just to check the level and another £50 to reset the ECU 'has anyone any idea please thanks tony