How does "Top up water for kettle" in Equipment Profile work

I have a small cooler box tun (with about 5 kg grains can only add 14 litres water).
To make a batch size of 22 litres I mash with 14 litres - empty tun - and batch sparge with 14 litres.
I then add 5 litres plain water to boil pot.

In my Equipment Profile I enter 5 L in "Top up water for kettle".
But I've noticed that if I change this nothing happens. Even if I make 100 litres the software doesn't pick it up.

Obviously I'm missing something here - can someone please explain how to tell software that I add water to the kettle after mash & sparge.

Regards
Mark

Where area you expecting this volume to show up? 

The program works volumes from the batch size back upstream to the mash.  When you enter in your 5 liters of top off water, it will deduct this volume first from the sparge amount, because this is the volume which floats (varies) in order to make the calculations balance.  You set the initial infusion in the mash profile so that is a fixed figure (or ratio actually on the grist amount in the recipe).  If you were to look at the volumes upstream of the 'top off water to kettle' you will notice that the program reduces the sparge volume by the 5 liters you entered for top off water.