1st and 2nd floor deck dimensions are different???

[Bill B]

This model has both a 1st and 2nd floor deck - one above the other and they should be exactly the same. The first floor model includes a deck that shows it measures 20' 2" X 10' 11". Then the second floor was created using the 1st as the reference. The 2nd floor deck indicates 20' 5" X 11'. What causes this difference?? Thanks, Bill B.