material calcs gone wrong

[rfcomm2k]

I have a drawing that was provided in response to my problem creating a room within an attic space. I refined it by adding some walls to delineate living space from actual attic space at the eaves. I then generated a material list.
First glaring question is where is 246 linear feet of 25 1/2" wall?
Second question is, where did all my wallboard go? between the "siding" and the "wallboard" sections there are only 25 sheets of 4' x 8' x 1/2" drywall. By my estimate there should be a MINIMUM of 66 sheets of 1/2" drywall, and that is a very conservative estimate.
What I discovered when I created a cross section elevation is that the north and south walls are only measuring 25 1/2" high, even though in the elevation and in perspective view they appear to be approx. 80" high. So I guess that accounts for the substantial amount of missing drywall, although these two walls only account for 75 1/2 feet of the 25.5" walls.
It would appear that in order to design rooms in attics, and possibly other odd shaped rooms (cathedral ceilings, A frame cottages, etc) you need to fool the program into accepting certain designs that don't actually calculate properly.
I know I bought the DIY version of the product, and I have no desire to upgrade to the high end one. But if a product is going to allow you to design a room with a cathedral ceiling you should be able to calculate reasonably well what material is required.
As a test I build a small 1 floor building 12' x 12' x 96" inside dimensions with a hip roof. Using standard 4x8 sheets that is 12 sheets of drywall. So I made a material list from area and set my cursor just outside the room and highlighted everything except the rooflines. I was told 13 sheets of drywall, not 12. So then I made a new list by room and this came up with 12 sheets. Where did the extra sheet come from? Certainly not from the eaves, or the exterior siding.
Well, now that I have vented enough lets get down to my actual question which is:
How do you REALLY build a room in the attic of a house with 1 floor plus the attic. Downstairs measures (rounding) 38' x 26' with 18" eaves and a ridge beam at 12' 3" from top of floor joists to bottom of beam. Gable roof, with no ceiling in attic, just drywall attached to underside of roof. Anyone interested in seeing the actual plan should explain to me how to upload it. I have zipped it down to 588K but the limit apparently is 100K. I will happily email it to you.