Hello nana . Welcome. I see this is your first post. Please take some time and swing over to Roll Call and introduce yourself so that we may give you a proper "Hello". All info you can provide us with such as smoker type, location and so on will help us answer any questions you may have. As for your question: Here is my opinion for what it is worth. Others will have different advice. This is only my opinion. I have cooked brisket for years. Unlike many here I do smoke mine hotter and faster. Hambone has got ya covered. Relax. Now. You say you checked your therm; which therm? If you are relying on the therm on your smoker, I can almost guarantee that therm is off, and by as much as 50 degrees in some cases. So you may be cooking more in the 300ish range. Not necessarily a bad thing with this brisket, just check out a good digital dual probe meat therm. As Ham said it's done when a meat probe or toothpick slides in like it was a warm stick of butter. If looking for sliced brisket you should start checking in the 180-185 IT mark. After wrapping in foil and resting for an hour it will hit 190-195 degrees which is just about right for slicing. For pulling ( being from Tx. I don't know WHY anyone would PULL brisket ) take it to the 190-195 IT then wrap and rest for AT LEAST 1 hour. Wrap in foil and a blanket. 2 hours better. Each brisket has a mind of it's own. Relax. Grab a cold beverage of your choice, sit back and enjoy the experience. Good luck. Keep smokin!