The file details pane displays various statistics and other information about the currently selected trace file.

A couple of the items may need some explanation, e.g.

Frames sliced: if there are frames in the capture that were cut short during capture this will tell you at what offset the frames were cut. If the cut is dynamic (e.g. using TraceWrangler's anonymization functionality to cut after certain protocol layers) it will just say "dynamic".

Time Order: if the trace contains frames with negative delta times (as can happen while capturing on 2 or more interfaces at the same time) this will say "out of order".