Count the total number of pendingDocumentWrites in a Firestore Collection

I would like to get the count of documents in a collection with pendingwrites. For unsent messages counter.

I did this but, every time I add a new message the count gets set back to one.

listener = firestore.collection("Chats").orderBy("timestamp", Query.Direction.DESCENDING).addSnapshotListener((value, error) -> {

    int count = 0;

    for(DocumentChange change : value.getDocumentChanges){

        if(!change.getDocument().getMetadata().hasPendingWrites()
            // Do some stuff
        } else {
            count ++;
        }

    }
    setCounter(count);

}