The sort indicators (those little 1's and 2's, etc. in the File List's headers) are not always shown, and even when not, sorting may still be occurring based on the view. Some of the explanation is esoteric and I feel this is an area for improvement.
If you want certain sort orders in the File List, then you'll have to a) most likely disable the Group By feature for the File List, and b) setup your own Sort order modifier in the view's Set rules for file display.
What you might want to do is create a custom view, perhaps a Panes view, and add the columns you want, including perhaps Bitrate for easy selection. Set the view's Set rules for file display to sort in the order you want.
(btw. sort keys are generally called Primary, Secondary, etc.)