Hi Brian,
There are two ways to perform a load calculation using the program. The first way is to obtain the dimensions of the home using the tracing feature. Different homes have varying degrees of zoom capabilities and will therefore have varying degrees of accuracy. However, in my experience the difference is usually 1ft, not 12ft as you are indicating. Note there is a overhang drop down on step 1 that allows you to account for gutters and other overhangs when making your trace. For example if you have a home that is 52X32 and you select a 12" overhang it will reduce the size of the home to 50x30.
Once you are satisfied with your traces you can proceed to step 2. Here you need to click on the blue system header and drill down into the zone -> room. The program creates a room for each trace you made in step 1. Once you expand the room section you will see all of your walls, windows, floors, etc. All of the inputs are completely editable.
The second option is to skip the tracing step all together and manually add your rooms and building components in step 2.
I suggest checking out some of our youtube videos here for more information https://www.youtube.com/channel/UC6c4tEhUWN6Yy6odPFrfIrg
If you still continue to have difficulties please create a help ticket and we will try to assist.
Best Regards
Bill