The new sales for eating/entertainment are based on square footage and historic UNP data. The new residents to the district are assumed to spend so much per year as well. By including both of these separately, Dr. D assumes that the New TIF district residents are NOT eating/entertaining in the TIF district. Also, existing Norman are not shifting spending from the Rest of Norman to the TIF.
Thus, the assumption is that the new spending is 100% by non-Norman residents or increased spending by existing Norman residents!