"Nearly There" is a Goal status that is in between "On Track" and "Behind." Once this status is enabled, Goals that are close to being "On Track" will appear as "Nearly There" instead of "Behind" so long as you are within the "Universal Goal Tolerance."
To enable this, go to Admin > System > Settings and turn on the Track Goals 'Nearly There' setting. You can set the Universal Goal Tolerance directly below there (0-100%). Note that you'll need System Privilege to access the Settings page.
The higher the tolerance, the more relaxed the "Behind" flag will be for goals across the system, resulting in more Goals that are "Nearly There" rather than "Behind."
You can customize the color used for the "Nearly There" status under Admin > System > Branding (see below). By default, it will have the same color as "On Track."
So long as a Goal's Current Completion is in between the dotted "Goal Tolerance Line" and the "Tracking Line" its status will be "Nearly There."
Adjusting the Universal Goal Tolerance changes the distance between the Tracking Line (solid line) and the Goal Tolerance Line (dotted line). A larger number in the Universal Goal Tolerance will increase the distance between the Tracking Line and the Universal Goal Tolerance Line allowing more Goals to be "Nearly There" than "Behind."