The trick is to check the box "I have many sales and would rather make summary entries" on the page where you check which types or "Box" of sales you have. Once you continue past this page (screenshot 2 in the answer), if you later elect to "Edit" the institution from the "Summary of All Accounts" page, that checkbox is never displayed for editing. I needed to delete the institunio and re-enter the data (which was not a big deal, since it was Summary data, LOL).
