Firestore - unexpected reads

It's impossible to know for sure given that we don't understand all possible routes of access into your database, but you should be aware that use of the Firebase console will incur reads. If you leave the console open on a collection/document with busy write activity, the console will automatically read the changes that update the console's display. This is very often the source of unexpected reads.

Without full reproduction steps of exactly all the steps you're taking, there's no way to know for sure.

Firebase currently does not provide tools to track the origin of document reads. If you need to measure specific reads from your app, you will have to track that yourself somehow.