I had this exact situation in September. Was awarded an R-24 line with R-days from Sept. 18 - Oct 6 (Oct bid month started on Oct 1.)
I bid for Warm-up/PC on the 23-24, and ALL R-days were dropped, INCLUDING the carryover ones.
You are first dibs at picking up open time trips in the View/Add window, though. Worked out great for me. Good luck!