Griffey Jr. Rookie Jersey's

[Griffey fan]

I have Ken Griffey Jr's "1989 Set 1" rookie jersey. I purchased it from Mill Creek Sports Cards and they got it from the Mariners. It is a size 46 and has 2 inches extra length.
I see that Grey Flannel has a Griffey rookie "1989 Set 1" jersey in their Dec. 9, 2015 auction right now. It is a size 44 and regular length.
I spoke with Grey Flannel about this and I was told players order more than one jersey at a time and there was probably several Set 1 (order 1) jerseys.
I don't understand why they are different sizes and different lengths.
Can someone shed some light on this for me please?

Here are photos of the jersey I have.