The blade set can be used on either of two sides, depending on the desired cut thickness:

The 38-blade set (item 19638) has 28 blades on one side, for 3-millimeter cuts, and 10 blades on the other side, for 10-millimeter cuts.
The 44-blade set (item 10644) has 30 blades on one side, for 3-millimeter cuts, and 14 blades on the other side, for 7-millimeter cuts.
The 60-blade set (item 11660) has 40 blades on one side, for 2-millimeter cuts, and 20 blades on the other side, for 4.5-millimeter cuts.