Last sample of a series before the report window — the seed the Home
UI (and the facade resampler) carries forward so sparse setpoint
series do not start the window blank. value is null (with a
far-future trigger sentinel) when the series has no prior sample.
Last sample of a series before the report window — the seed the Home UI (and the facade resampler) carries forward so sparse setpoint series do not start the window blank.
valueisnull(with a far-futuretriggersentinel) when the series has no prior sample.