When I run report_datasheet on my design, I do not understand how the column Source Offset to Center is being calculated on a bus.
The Source Offset to Center is the difference between the center of the data eye to the center of the data capture window based upon worst case setup and hold times of the input pad.
To calculate the Source Offset to Center for each bit:
The Source Offset to Center is then calculated by subtracting window #1 from window #2.
In the above example, it would be 3.5 ns - 0.5 ns = 3 ns. Ideal Source Offset to Center would be 0 ns, and it may be beneficial to add an additional 3 ns of set_input_delay.