I've never done such a small brisket, but I've heard stories that those little ones can actually take much longer per pound than a larger cut. The official answer is that it's done when it's done based on internal temp and jiggle. With that cut I'd set at base expectation at 7.5 to 10 hours.
This document from Smokin-It will come in handy. I have it downloaded with a shortcut on my desktop.
https://www.smokin-it.com/v/vspfiles/files/SmokinTimes.pdf
I've done 2 small brisket flats. The 4lb took 12 hours, so 3 hours per pound. I did a 2.5 lb that took 9 1/2 hours. I did a 3.3lb tri tip like a brisket that took 9 1/2 hours. I have been told it is based more on thickness than weight.