The marker with the segment that contains bad data should have a peak or jump that matches the black region.
The area between either the edge of the original data segment and its start or end is colored light green.
To extend a data segment or gap in the Optical editor, M-click and drag on the edge of the area to be increased.
The light green segment is re-interpolated, removing the noise and updating the Quality Bar. Continue searching for other black areas at the start or end of data segments.