Your Preferences > Settings > Clear Area value is set to zero but on some designs calculated by Content Dimensions, Crate Pro 6 adds additional 4" to each side of the entered content dimensions.

So 8" is added to the Length and Width and 4" to the Height.

Crate Pro 6 may not always see the Clear Area value as '0' so will default to the original values when the program was initially installed. Change the Clear Area value to a minimal number such as .001 or .01.