you are not in the business of selling sports tickets. This makes them capital assets where the gain is reported on Form 8949/Schedule D. You need to link the 1099-K to Schedule D. Then use the link to the capital asset sales worksheet to report details. The proceeds are automatic from1099-K
date sold, date acquired, cost including any fees, are required. The 8949 box would be C since no 1099-B filed with IRS and neither was your cost. likely short-term