It's the difference between 'live' data and data from the logger and/or Cumulus data files when you start Cumulus up; there's only one wind direction value to plot for 'historical' data (so the two plots coincide).
If the data came from the logger (e.g. after a period where Cumulus wasn't running), the station only stores the current direction, and Cumulus doesn't try to calculate an average as there are so few data points. If the data was live at the time but has been read from the log files at start up (e.g. you just restarted to install a new version), then in this case there's only the average direction; Cumulus doesn't bother storing the 'current' direction, as typically it's of less use compared to the average - as you've no doubt seen, the 'current' direction tends to be all over the place with a Fine Offset station.
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Steve
Sanday Weather----------------------------------------------------------------------------------------------------------------------------------
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