How does the dot in the 2D results/behavior graph work? My staff don't seem to get it.

The 2D dot is a subjective tool, but it may be helpful to think of it this way: if the dot is in the middle, then that means the person has done a good job based on what his role and seniority would indicate.

If a person did better than expected, the dot belongs more towards the top right corner, and if the person didn't quite achieve what could have been expected of him, then it should be more towards the bottom left corner.

Discussing with your team across departments what the dot or rating means to them, helps to align the rating in order to compare results across teams. If your staff still feel unsure about it, you can disable the results/behavior graph in the settings for the performance review.