Subsegment lengths are automatically modified when Street Segment Length is adjusted. This is true if the Length is adjusted in Lucity or from GIS updates
If the new Segment length > the old Segment length then the length of the last subsegment is increased and the "stationing" is adjusted.
If the new Segment length < the old Segment length the length of the last subsegment is reduced by the difference. However it will not shrink smaller than 1 foot.
If the last subsegment has been reduced to 1 foot and there is still a difference to make up the difference is subtracted from the length of the next subsegment. This continues as needed.
If the length of all subsegments have been reduced to 1 foot and there is still a differece to make up an error will appear.