I am doing my first brisket and I got it a Costco’s it is 4.5 lbs and about 3-4 inches thick. The thermometer in the Lg. Egg says 250 and its been on for 2.5 hrs. meat thermometer says 190…..is this possible? I have moved the thermometer in the meat to a second location same reading. Both thermometers have been calibrated using boiling method....HELP…is it done?