Nope, not stupid at all. This is a very common issue with InfluxDB. It takes the data type from the first message you send it. It then will not change it.
To be honest, if you are just getting started, I would recommend dropping (deleting) the whole database and starting again.
Here is an article I posted ages back about terminology and recommended structure in InfluxDB in case it helps. Need more detailed information on influxdb - General - Node-RED Forum (nodered.org)
And don't worry, InfluxDB is mind-twisting to get started on but once you've set it up, it all "just works".
