Now you give is info that the subject lot is 20,000, but the lot sizes of the comps you used are 14,000, 7000, 9000 sf - the subject is on a lot that is dividable for subdivisions and valuable -
did you find any sales on a 20,000 sf lot range - 18,000=24,000 sf lot?
A comp is a similar sale, not just any old sale - and while a house on a 7000 sf lot can be a comp, it would need a huge lot size adjustment and there should have been, if possible, comps on lots near the subject lot size -
do any exist? did you look for them? The comp on the 14,000 sf lot is the closest in lot size to the subject subject...what did it sell for vs the ocmps on smaller lots?