The red arrow indicates the limit that could not be passed beyond during any incubation.
Depending on the assay tube used routinely in laboratories, it could happen that the limit line indicated on the sticker could be overcome. It cannot give rise to any problems on the result itself, provided the limit indicated by the red arrow on the figure is not passed. The gold conjugate is placed at 2cm from the bottom of the stick. Incubation limit should not exceed 1cm, i.e. the green line indicated on the figure.