Boil size calculation not adding up I think

I don't know if its something I'm doing wrong or a limitation of the software, but once I pick my equipment the boil volume doesn't change no matter what ingredients I add.  If I used 4 pounds of DME or 15 lbs of LME I still get that I need to have a 6 gallons pre-boil volume.  Am I expecting too much or doing something wrong?

Thanks in advance for any info,
-Wes

I don't think I understand your question.  Why would you expect your pre-boil volume to change based on ingredients? 

Pre-boil = batch volume + trub loss + boil-off

Now, if you are talking about WATER required, yes that will change based on LME vs. DME, and other factors when talking about all-grain or mini-mash methods.  But, once the extract is in the water, and you have wort....you should have the same amount of wort in the kettle each time. 

I'm with Tom here, not sure I understand.  Boil volume is completely based on the batch size.  You should expect to see the water needed fields changing based on the ingredients you add to the recipe or the type of recipe (extract vs all-grain).  If for some reason we are totally missing what you are asking, would it be possible for you to attach some screen shots so we can see what you are seeing?

Cheers!