1099-K received from RUNSIGNUP, INC for booster club

Hello, 

I received 1099-K issued to my LLC EIN from RUNSIGNUP, INC. Except, I let the booster club used my LLC EIN to conduct their fundraiser for races. I already filed my personal tax return but didn’t include the 1099-K, since it’s not an income for my business. How do I report this? Thank you for your help.