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avast doesn’t run a scan just out of the blue.
You (or someone there) must have told avast to do so.

There is no need to pay for avast passwords.
It is free in all home versions.
If you don’t want it, don’t install it (or remove the component)

You very likely have more than 9 passwords stored on your system.
Even if you don’t use them (anymore) avast will still detect them.
There is also one (likely even more) passwords on the router/modem.