The unit for the X-axis value is defined with:

Active-Motion-Settings > Motion tab > Motion Units > X-axis.

The default unit is degrees.

SEGMENT-EDITOR - X-axis Values - Segment-Width Parameter

Segment-Start (Read-Only) : The X-axis value at the start of the Selected-Segment

SEGMENT-WIDTH (Read-Write) : Enter the Segment-Width for the Selected-Segment

Segment-End (Read-Only) : The X-axis value at the end of the Selected-Segment

WARNING:

When you edit the Segment-Width you also edit the Motion-Width.

If you do not want the Motion-Width to change, you must also also edit the Segment-Width of a minimum of one other Segment.

See also: Segment-Range, Segment-Parameters,  Y-axis values