Just forget the problem. The maxium allowed gap between graducation and OPT is 60 days. You may have a status gap of 20 days, which won't be a problem to your EB 485.
Furthermore, if the gap is caused by CIS (CIS approved your OPT later than you requested), no gap at all.
Furthermore, if the gap is caused by CIS (CIS approved your OPT later than you requested), no gap at all.