For CAS with part number: 938XXXX and 939XXXX you will get this warning message (4 parts numbers only) because this CAS with EWS5 security. Other parts numbers (Like 928XXXX,927XXXX and 926XXXX) are 100% safe (EWS4 Security).
Anyway, If you have a BDM tool, don't worry...just go forward. what ever will happen, we can recover it for you.
Cheers