TDM400P module configuration?

This is actually a Digium hardware question, but didn’t see a forum for that…

So, I have purchased a few TDM400P cards with 2 and 3 FXO modules… Why did they all come with the modules starting in 4 instead of 1? meaning, a 2 module card came with 4 and 3 installed, and the 3 module card came with 4, , 3, and 2 installed? Is there a reason for this?

Just curious.