Use Frame Horizontal Extents to show only the active time segment, and use Frame Horizontal Extents Keys to show all keys, including those outside the active time segment.
To display the active time segment in the Key window:
The active time segment (lighter background color) is centered in the Key window.
Adjusts the magnification of the Track View Key window horizontally so that all of the active time segment is visible at once.
Scales the Track View Key window horizontally to display the full range of all animation keys. Depending on your animation, this view could be larger or smaller than the active time segment.