Please make sure you are adding the correct record as changes of A record might need at least 4 hours of propagaion period.
You could like to add record as below where will point docs.domain.com to IP of 127.0.0.1
docs IN A 127.0.0.1
1. Log into HELM Control Panel.
2. Seek for your domain.
3. Select on DNS Zone Editor.
4. Select "Add New" for new creation or click on the old record that need to change for modification.
5. Please use the format as below.
Record Type: A (Host Record)
Record Name: docs
Record Data: 127.0.0.1
Record References: 0 * MX records only
6. Click on Add/Save.