An optional feature of the Nedap PorkTuner system is marking. With marking certain animals can be recognized and marked, based on the weight or growth of the animals.
Select the menu item Marking.
In the field Start marking action, click on Growth when a marking action based on growth must be entered. Click on Weight when animals with a certain weight must be marked.
Fill in the date when the marking action should start, which color should be used, and when the animals should be marked.
Select the location(s) for which the marking action is, and click on Save.
As long as the marking action is ongoing, the progress is visible on the Dashboard in the Marking widget.
Recent markings can be viewed by clicking on the menu item Marking. Select current actions or actions that are already planned (Now / Planned), or actions that are finished (Finished). Click on the arrow icon 
to see the details of the action.
When using spray markers, an additional licence is necessary. Probably this is not activated. Click on the My Portal icon in the upper right corner of the screen to activate spray marking.