datasheet dimensions
REF designates a reference dimension and is provided for convenience only. If you look at the drawing carefully, you can work out all the reference dimensions from the main dimensions.

For example, to get the pad height, take the leg span (3.85), subtract the distance between pads (1.4) and divide by two: (3.85-1.4)/2 = 1.225.

You should try to follow the main dimensions when designing a footprint, even though it may not be the most convenient method in the PCB footprint editor.