Problem with my oven on the GE electric stove less than a year old. Model # JBP350 M2WW. When I set the oven for 350, then 15 minutes later it beeps, that it is ready. I used an oven thermometer which read it was only 240 degrees, it took another 1/2 hour to get to 350. Is there a way for me to adjust this, so that it beeps when it reaches the set pre-heat temperature?