On the Home Page Graphs/Charts the values of the parameters being graphed are identified by the colour of the lines and also by the shape of the individual points (round, square, diamond etc). However in the legend although the individual parameters are identified by colour, the same shape (round) is used for each parameter rather than the one used on the actual chart. For example in the chart below the values for Sonoff 02LD-1 are indicated by the lighter green line and and round shapes in the charts, similarly those of the values of
Sonoff 02LD-2 are indicated by the blue line and diamond shapes in the charts and those for Sonoff 02LD-3 are indicated by the darker green line and square shapes in the chart. In the legend however the same shape (round) is used for all three (you may need to "zoom in" to distinguish the various shapes on the chart). It would be better is the shape used in the legend matched that used in the actual chart.
