Ski manufacture is not a perfect science. There is lots of layers, resins, natural materials (wood core) so there is lots of room for variances. When picking and matching skis for pro atheltes manufacturers put in a lot of effort to put together "pairs" using all kinds of meaursements. In the shop you likley cant do that, but you can do a few things, to pull a "pair", not just the next two off the wall.
2mm is a big difference, and likley means one is at one end of the quality control range, and the other ski is at the other end....or possibly one is just out. Having said that will you notice it? Depends on your skill level and where you ski. Chances are thou....you wont notice.