Don't worry for one second about having reported less individual sales than reported by the 1099-B. The IRS's "matching" process certainly doesn't work on a line item by line item basis. If you report your sales correctly, even if you break one sale into 10 trades, (e.g., you're reporting each and every lot that went into the trade), the IRS simply can lay a glove on you. Reporting your income correctly pretty much makes you bullet-proof, no matter how the detail is entered into the income tax return.
If you've just got to use the RSU step by step interview for some reason then report the 2 sales as:
Vested: M-N
Sold for taxes:0
Shares sold: M-N
and
Vested: N
Sold for taxes:0
Shares sold: N
That gets your "vested" number correct (M-N+N=M) and your shares sold correct, (ditto).
