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I wouldn't trust it.... I think my Char-griller therm was off by about 40-50°. Buy a couple of 2" or 3" dial therms and install them on the left and right side of the cook chamber about 2" above the cooking grates.
You can use one you know is correct and test different spots and note where the built in one is at different temps. As long as they're consistent you'll be good.
I've got a char broil charcoal offset that I know where 220 to 250 are by comparing.