How to program Fiverr withdraw button?

I am wondering if anyone has experience using Freelance site like Fiverr and has experience how the seller withdraw button works in the backend.

Say, for example,

1. A seller has earned $150 on Fiverr.
2. Fiverr takes 14 days to clear the fund.
3. After that, the seller can click withdraw Paypal Account button.
4. The fund will automatically be sent to the seller's Paypal account .

How does the backend works for Step 3 and Step 4?In my observation, this happens instantly without any Fiverr CS. I feel like the cleared fund is sitting in Fiverr's account. When a seller click withdraw, the cleared fund will automatically be sent.

Thank you in advance for any ideas.

CheersMarco