tiny rubber gasket on expedition watch, to go under crown?

I just assembled the sapphire dial expedition kit and it seems to be working well, but after assembly, I noticed a tiny rubber dial, which looks like it might go under the crown, for extra water proofing?

There was nothing in the assembly videos about it, so any help would be appreciated…

Photo would be helpful here

My guess is it’s something that fell out during assembly?

I found same thing in my NH34 GMT Dive Watch kit. Sorry I’m new to form, I took pictured with larger gasket from case back but was not able to post it. Get permission error. Assuming goes under crown but haven’t found any mention in videos

I had the same thing with my GMT kit. I was told it actually goes on the little aluminum knob on the spring wire loupe holder/head piece gizmo…