So I had a designer come professionally measure my house and draw up plans last year. I'm trying to do my own plans now based on hers and realized that the main floor (street level) in the arch drawings is 40 feet wide internally and the bottom floor is 38 feet wide internally. I have double checked her measurements and got the same numbers (and I am accounting for internal bedroom and bathroom walls). Is this even possible? What am I missing? Our house slopes down a bit to the backyard but no real basement/underground walls.

This is frustrating because now I am looking at a 2 story addition and can't figure out how to transpose it.

Ideas?