Please make sure you are adding the correct record as changes of CNAME record might need at least 4 hours of propagation period.
You could like to add record as below where will point docs.domain.com as
CNAME to ghs.google.com.docs IN CNAME ghs.google.com.
1. Login to your Website Panel via http://cp.domain.com or through http://serverhostname.com.
2. Click on "Domains" under system.
3. Choose the domain that you wish to modify your domain.
4. Click on "Edit DNS Zone Records" .
5. Click on "Add Record" to add new CNAME record or click on the "Pen"
logo icon on the left side of the record to edit.
6. Please use the format as below. Remember to click "Save" to save new record and the you have made.
Record Type: CNAME
Record Name: docs
Record Data: ghs.google.com