Hi richriverfarms,
If you have Long Service Leave's Payment Setup set to Report the earnings for the leave taken against another pay category, the earnings line will automatically be applied in the pay run, set to the pay category you chose in the drop-down menu (for this, it will likely be Long Service Leave Taken).
If you have the Payment Setup set to Basic, the earnings line is also automatically applied, and by default the pay category will be the Default Pay Category of the employee (such as Permanent Ordinary Hours).
The only way that earnings are not automatically applied will be if you set the Payment Setup to Don't pay for the leave taken.
Hope this helps!
Bonny