That’s the long link inside the QR code (https://pracproof.co.za/verify#…) — paste it from an email, WhatsApp or a QR-scanner app. The short code printed on the document (like 53F6-49FD) can’t be checked by itself; after a scan it’s shown so you can match it against the paper.
Verification is done entirely on your phone — no data is sent anywhere. A valid result confirms the document was signed on the issuing doctor’s device and has not been changed. It does not by itself prove the prescriber’s identity; confirm that against the HPCSA register if needed.