It's impossible to be sure without seeing the directions that come before and after this one, but here's my interpretation. They want you to cut three strips 3.5 inches wide, making sure your cuts are accurate. Of those three strips, you will use only 2 and one-half of them for the pattern. If you notice, there is no "inch" after the 2-1/2; this is the tip-off for me that they want 2 and one-half strips. I would verify this with the instructions that come later, though.