Nothing like wasting a cut, averything seems right till you pull it out of the miter box and hte ange is reversed!
I just finished a kitchen, fairly easy, (it would seem), 5 inside corners 1 outside corner. I actually finished and didn't have to go buy more. I did have to cutr a slice and insert it however, wood putty and paint fix many ills. Hate to think if I were using cherry.