This html test page will store the continuous 10,000 values to the path /Test_Stream/Stream
In your Arduino code, set the stream path in Firebase.beginStream to /Test_Stream/Stream

And the stream callback function test code.

void streamCallback(FirebaseStream data)
{
if (data.dataType() == "int")
{
Serial.print(count);
Serial.print(" ");
Serial.println(data.intData());
count++;
}
}

Tempolary set the database rules in the Firebase project console to allow full read and write.
{
"rules": {
".read": true,
".write": true
}
}
Press the Set button to store the 10,000 values to the Firebase RTDB.
Press the Delete button to delete the previous set data from the Firebase RTDB.
Don't forget to change projectID and Web API Key in the source of this html file.

Check the values received in the stream callback function that will get all of these 10,000 values changes.