1. The exact bp number of your PCR product including from 366 (C) to 77 (T) is = 366-77+1 = 290, not 289.
2. It also depends on which kind of DNA polymerase you use. Some (for example, Taq DNA polymerase) will add one extra non-template-based base (3'-overhang A) at the end of your PCR product. Some (for example, Pfu DNA polymerase) will not.