You bowled 10 strikes in first 10 frames Second ball of 10th frame was 9 the 3rd ball was o why was my score 288 instead of 289?

288 is correctA strike is scored 10 pins plus the total of the next to balls thrown. Your 8th frame score is 240 after you threw the 10th strike. The ninth frame strike adds 10 to 240 plus the next two balls thrown in the 10th (X-9) brings the 9th frame total to 269. Close the 10th frame with 19 (X-9-0) your final score is 288