Auto check-in is designed for the scenario where you have a physical line of ppl waiting to be checked into class. Class is about to start, and you'd like to expedite each customer through.
Some customers are already registered. They just need to be checked in. Simply search the sign up list and flip the toggle next to their name.
For those in line who have not yet registered, you'll need to register them, then check them in. By flipping on the the 'auto check-in' toggle, you can skip this second step. Ie. anyone you register will automatically be checked in.
The Auto Check-in feature allows you to skip step 2 of this process. It automatically checks them in, eliminating the need to go search through the list for the customer.