PCB Footprint Design Dimensions
The 2-2.00 dimension (your Y) is 2.00mm, but it applies to two identical holes (2-) on the datasheet. Only one of those holes is dimensioned for length, the other is dimensioned for width, to avoid an excess of lines and dimensions cluttering the drawing. You are expected to figure out which pair of holes are the same size from the symmetry of the drawing.

Similarly, the socket has 4 tabs 1mm wide, X, shown as 4-1.00