Please help, how do I get 720x576 format output video?

Hi, I am new to pI3 so maybe this is easy thing, but I cannot get my video out of PI3 in 720x576 format. In Project Settings I changed Stage Size to the required size but in the fields next to it the ratio is 640 x 480 and even if I rewrite it and I save it, the next time it is back to the original values, not 720x576. When I go to Save Output than the resolution indicated, at 100%, is still only 484x414.Why? Could you please tell me what to do about this? I want to use the video in AE later on. Thanks a lot for help.