Assuming that is a rephasing cylinder, then the blue seals on the pistons uncover a bypass port or short linear grove in the cylinder barrel bore to allow oil to bypass at one end of the piston stroke.  With that situation and the blue seals offset to the thickness of the pistons, then it would matter.  Also, the barrels likely only have the bypass grove at one end so they need to be assembled with the notched ends at the same end of the assembly as before also.