The first box will remove the Safelinks protection from URLs that begin with "https://gcc01.safelinks.protection.outlook.com/?url=".
Copy and paste a safelink into the box and click Decode which will provide you with a Proofpoint URL.
The second box will decode URLs that start with "https://urldefense.proofpoint.com/v2/url?u=".
Copy and paste the decoded link from Step 1 into the box and click Decode, giving you with the original link.