When doing RX Margin analysis on an IBERT design that uses multiple line rates, the GUI can present results with improper scaling.
The horizontal range of the scan result is determined by the RXOUT_DIV attribute of the channel being scanned. In an IBERT design with multiple line rates, only the first channel's RXDOUT_DIV is used for scaling, and the horizontal range of the scan results will be incorrect for other channels. Even though the scaling on their presentation is incorrect, the results of each scan will still be valid.
This is currently a known issue, and it will be fixed in the 14.4 version of the tools.