“Are You All Set?” Means “Are You Ready?”

“Are you all set?” commonly means “Are you completely ready?” Here, set means ready, not “configured”.

A: Are you all set to leave?
B: Yep, I’ve got my keys and phone.

It can also mean “Do you need anything else?” If a staff member asks, “Can I help you, or are you all set?”, they are checking whether you require further assistance. Both senses describe a state in which everything needed is already in place. When the earlier conversation is about leaving, it asks about readiness; in a service encounter, it asks whether anything more is needed. The expression is natural in everyday Australian English and common in American English as well.

https://www.merriam-webster.com/dictionary/set