Custom Board Editor Pawn Promotion Bug

There is a bug that seems to appear after changing the board size. 

In the shown position above, White is able to promote the Pawn. However, the Pawn would be on the 5th rank, but the promotion is set to the 7th rank, so what is happening here? Additionally, the notation on the right is not even accurate...

This is because the system thinks that the position actually looks like this: 

...as noted by the correct notation and proper promotion. 

Clearly, this is misleading. This bug needs to be fixed. 

a 10x10 board is a 14x14 board with a bunch of walls on the edge.

Okay, that’s the “what”, now answer the “why” - why is it like this?

It's there to make editing the board easier. Sometimes if you want to start with a regular 8x8 preset, but want to expand the board to the left, for example, if it began with a,b,c,d, 1,2,3,4, then that's not possible. You would then have to go through the whole tedious process of shifting every piece x squares to the right. If it is in the middle, however, then it becomes far easier to extend the board to the left, and maintain symmetry as well