Thanks so much Bhoomika!Agreed, I can't think of a reason it can be negative and being that scAdd and purchase are event counters, they can only increment so nothing a dev could mess up such as sending a negative counter to the dataLayer or so.... 

Hello, Is there a reason other than incorrect implementation (sending negative values) that a  cart abandonment rate could be negative?I did not see this in real life, I was asked about it in a job interview question.Thanks!Rafael