All digits in the PCI field are masked. This means only agents/admins who have access to unmask/edit the PCI field can view the content in the field. Partial masking is not enabled as we don’t want to restrict you to use this field only to store/handle card information and be able to use it to their edge-case requirements.
Also, storing the last 4 digits of the primary account number (PAN) can be done on a separate field and does not violate any PCI DSS compliance rules.