@Janine86 Sorry to hear the host cancelled! The credit offered as a result of the cancellation is included when you rebook automatically.
This applies if you chose to have your refund applied to another reservation and the new reservation costs more than the original, cancelled reservation. If you indicated that you wanted a refund made to your payment method, no credit will be applied. Also, you must re-book within 30 days.
Here is a link that goes into more detail about the eligible credit:
https://www.airbnb.com/help/article/950/i-received-an-additional-credit-after-my-host-canceled--how-...
I hope this explains!