Yeah, that is a tricky one.
From an EyeX software viewpoint, the calibration process is able to compensate for some vertical and horisontal offset. The calibration would probably be able to compensate for the small vertical offset if the eye tracker was mounted just above or below the buttons in the center. It might also give a reasonably good result if the eye tracker was mounted to the right or left of the buttons, but this offset might be too big to get good tracking on the side of the screen furthest away from the center of the eye tracker.
Whether the mounting bracket would actually be able to hold the weight of the eye tracker if it was attached protruding above or below the frame of the monitor, I cannot say. I’m guessing a couple of millimeters above or below should be fine, but that is just a guess.
Before attaching the mounting bracket, I would try different positions just holding the tracker with a steady hand and do a display setup and calibration, and choose the position with best tracking result.