You are mixing up boxes, columns, and codes.
Near the top of Part II of Form 8949 there are three checkboxes labeled (D), (E), and (F). Box D is checked, indicating long-term transactions for which basis is reported to the IRS. That box D at the top of the page applies to all the transactions on that page.
In the list of the individual transactions, there is a column (f), not box F, for adjustment codes. Your first transaction has adjustment code D in column (f). That adjustment code D has nothing to do with box D at the top of the page. Adjustment code D indicates that you had an adjustment for accrued market discount on that transaction. The other two transactions have no adjustments, so there is no adjustment code in column (f) for those transactions.
You don't have to change anything or override anything. It's correct the way it is.