What is the procedure for collecting the last 30 days of a COVID extension and do I need to cancel it before flying out?

I have an under consideration stamp for a covid extension and need to go to Laksi on May 11 to get the last 30 days of the extension. I have a few questions:

1) What is the procedure when you're returning for the extension balance on an assigned date? (Do you need to get a queue number from the document check desk? Do you need to bring all the same documents again, and fill out the covid extension request form again?)

2) I am flying out on May 19th. Do I need to cancel my covid extension or otherwise do anything? Or can I just leave?