In comparing a widget showing current AQI to a widget (identical sensor) showing raw PM2.5µg/m³, it is clear to me now that the data do not actually match because the raw PM2.5 being shown does not include the fractional portion of the data. I can see the fractional portion if I hover my mouse over the map’s graph. So I know it is there but not being shown.
It is also clear that the raw data being used to compute the associated US EPA AQI makes use of these fractional values. So for a given displayed PM2.5, the displayed AQI will vary. I have checked and the AQI is correct for the actual raw PM2.5 data with the fractional portion included.
I think it makes good sense for the PM2.5 layer widget to include the fractional portion so that the AQI displayed in the corresponding AQI widget makes sense. There is plenty of room in the widget to include this data and I see no reason why it should not be included.