The pattern piece for the COVER is the correct size, however the size notation on the pattern piece is incorrect: it should be 5.5 x 3 inches instead of 5.5 x 3.5 inches. To correct your pattern all you need to do is cross out the 3.5 and write in 3.
Again, the pattern piece itself is the correct size, it's the pattern label that is incorrect. Let me know if you have any questions! Sharp eye, Melissa!