If you chose monthly you should have seen just the taxes charged, as that’s what happened with both of my orders set to monthly on my Apple Card.
I’d say wait it out and if you receive the watch before seeing that charge reversed just return it to a store within the return period and see if you can purchase one there. Supply should be replenished by then.
Also, if you have the Apple Store app, you should see this under your watch order:
Basically as @Knowlege Bomb showed a screenshot that's how much you will be made responsible monthly. Of course if you already have a balance on your Apple Card that goes with it on top of the monthly plan.