Columns, Whole, Zoom In, Zoom Out, Analysis; are the same as the regular sequence display. Assembly, Arrows, Quality, DNA are specific to, or modified in the assembly display.
By clicking on the Zoom In button several times, the arrow heads of
the Trace Assembly column expand to show intervals. The direction of the
read is indicated by the direction of the arrow. The small circles at
the top and bottom of the column indicate that the read extends beyond
the window display area.

Clicking on the "Quality" button displays the regions of sequence
conflict on the Trace Assembly lines, red for miss matches and blue
boxes for insertions. The
contigs column also changes to indicate the relative coverage on both
strands.

you bring up the sequencing traces themselves.