Strange volumes given in batch sparge

Can anyone explain why it wants a tiny sparge of 2.5 L and then a much larger one of 13.5L? my cooler is 38L so is plenty big enough. I'm actually doing a 5gal batch in my 10gal kit

In your mash profile, you most likely do not have the box checked to 'drain mash tun before sparging'.  So the program tops off the mash tun, assumes that you drain it and then adds the rest of the sparge water.  In short, the program only does what you tell it you want to do.

Thanks for that! Never even knew that setting existed