Meanings of the Alignment_3D items?

Hello,

We are curious about the meaning of several data items found in the alignments3D category. We noticed that some of them seem to have a value other than 0 or 1. Can someone share some insight? Thanks.

Here are some of them found in a 3D-classification job:
alignments3D:
error
error_min
resid_pow
slice_pow
image_pow
cross_cor
alpha
alpha_min
weight