Single element produces multiple lines on graph

Using Grafana 9.1.6 on Linux I am trying to chart some data in a time series. For reasons I can’t understand this single metric is producing two seperate lines on the graph. So here are some images to show what I mean…

Given this data…

And this query…
rate(container_memory_usage_bytes{name="go2sim-tele2-sessiondata-consumer"}[10m])

Why do I get 2 lines and not the one line I’m expecting?

Thanks for any help you can give me.