[webauthn] What does it mean to "get assertions" in getAssertion step 7?

bzbarsky has just created a new issue for 
https://github.com/w3c/webauthn:

== What does it mean to "get assertions" in getAssertion step 7? ==
https://w3c.github.io/webauthn/#getAssertion step 7 says:

> For each credential C within the credentialList that has a non-empty
 transports list, optionally use only the specified transports to get 
assertions using credential C.

What does that actually mean?  Shouldn't this be handled by 
authenticatorGetAssertion?  Or is this a limitation on which 
authenticators should be talked to at all, and the clause means to go 
on to the next authenticator?


Please view or discuss this issue at 
https://github.com/w3c/webauthn/issues/281 using your GitHub account