The sleep disruption overnight severity message gives the overall level of sleep disruptions detected during the night.
timestampDateTimeMoment the message refers to, in UTC. FIT stores it as seconds since the FIT epoch (December 31, 1989, 00:00:00 UTC); decoders usually expose it as a regular date.
severityEnumOverall severity of the disruptions: none, low, medium or high.
nonehighlowmediummesgNumStringGlobal message number identifying the kind of message. Decoders use it to know which profile to apply to the data.