Hi Batz,
At this stage BS looks at the entire sparge as one quantity of water -- I presume PM is similar.
I think Brad is considering this for the next update ..... don't quote me though.
In the tools section select "water needed" and work through the mash and boil sections. On the right hand side of that tab you should see the exact amount needed for you entire sparge.
If you are batch sparging try to balance the batch volumes into the boiler.
On another note -- did you try [not] preheating your tun and if so did it help?
I tried loading that file you sent without any luck. I will contact Brad and get some advice.
Steve