Are you talking about the outline of the A4 paper or the outline of the press platen itself? The latter is quite normal and will normally disappear when the tee is washed for the first time. The edge of the paper itself may also leave a slight impression but that too will disappear. Getting the pressure right is something that will only come with experience. If you have insufficient pressure the image will not transfer fully. Have excessive pressure and you may find fleks of colour outisde the main image area.