You have 15 hours to withdraw your design or challenge the report before it's escalated
If you challenge the reports then the dispute is escalated to 99designs who make the final decision (there is no appeal process). Should you be unsuccessful then you might be suspended from 99designs and possibly banned.
If you choose to withdraw your design you will not suffer any consequences.
Before acting it might be pertinent to review our Designer Code of Conduct to understand where we stand on these issues.