Clarify comments in configuration loader

The original comment used words like "higher" to mean "physically above another element" and "lower" to mean "physically below another element" but the list was numbered in increasing order, so item 3 was 'lower' than item 2 (isn't that confusing when 3 is lower than 2, but 3 is greater than 2
numerically). This is extremely counterintuitive for people who assume "higher" means "numerically larger/greater", and "lower" means "numerically smaller/less."

This PR changes the comment to use "top" and "bottom" of the list, and avoid descriptions that contrast physical list layout with numerical ordering.