A work vehicle includes a work implement. A control system for the work vehicle includes a controller. The controller acquires an end position and a target distance of work performed by a work vehicle. The controller determines, as a start position, a position that is away from the end position by the target distance. The controller generates a command signal to start work from the start position toward the end position and to operate the work implement according to a target design topography. The controller modifies the target distance based on a result of the work.