Correct, 12 seconds / 12000 ms is the max delay time. With some extreme circumstances the pedal will display values beyond this as you have found, but the max delay time is fixed to 12 seconds.

And yes, Cosmic Web is a very versatile multi-effect! If you try the Repeat A/B perform parameters you can use it as a dual looper. An example of that can be seen here: https://youtu.be/0jEvzZPuzbU?si=PYWOh9jiX9MHHIdj&t=106