You can customise the free of charge in the dropdown. This is useful if you want to extend the default list of reasons. These are potential reasons that a job may end up being marked as free of charge at any time. In order to add one, open your system settings and click into 'Free of charge reasons' from the 'Jobs' section.
You will see a form on the left-hand side and a list of existing free of charge reasons on the right-hand side. You can add your new free of charge reason on the left and it will appear on the right when you click 'Add free of charge reason'.
Once added, you can edit these if need be using the 'edit' function on the right-hand side, likewise with deleting them. Simply click, drag, and drop the free of charge reasons to reorder them. If you want to move a free of charge reason from page 2 to the top of the list, then change the number of free of charge reasons showing per page to 10 or more (depending on how many free of charge reasons you have).