Hi Eric,
Great news that it worked out!
There can be some offset in the calibration depending on how well the eye tracking algorithms are able to model your eyes. But it could also be due to something else more specific to the EyeX Plugin for UE4.
Go to the EyeX Settings (can be found by right-clicking the EyeX icon in the task bar), and click the Test Eye Tracking button. If the offset is the same in this test app, the problem is with the calibration. It might be improved by re-calibrating, but it might not. If there is no offset in the test app the same way as in Unreal Engine, then there is something specific for UE going on.
We have had a known offset problem in UE4, where you would have to use a workaround and move the mouse over the game window once in order for the EyeX Plugin to be able to update with correct coordinates. I’m not sure if UE4.7 includes a fix for this or not (our pull request was rejected and the UE team went for another solution which I haven’t had the chance to try out yet). So, you could try and see if it helps moving the mouse over the window.