I think you may have to do a split stay, so your "2d" reservation falls in the discount window. IIRC, room only discounts can't be applied early. The only "outside the window" application that I've ever heard of was FD if you check in during the discount window, but the stay goes into the blackout. I'm quite sure someone will chime in and let us both know if I'm wrong.....
Karlzmom is correct. They won't honor the room only promo that starts on 8/15 if you arrive on 8/13. You would have to book two separate reservations - the first res would be for the nights of 8/13 & 8/14, and the second res would start 8/15 and would have the promo applied through the rest of your stay.
Note that you will have to check out/check in again and might have to change rooms for your second stay.
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