The presence of the RR-Interval field is dependent upon bit 4 of the Flags field.
The RR-Interval value represents the time between two R-Wave detections.
Because several RR-Intervals may be measured between transmissions of the HEART RATE MEASUREMENT characteristic,
multiple RR-Interval sub-fields may be present in the characteristic. The number of RR-Interval sub-fields present
is determined by a combination of the overall length of the characteristic and whether or not the characteristic contains
the Energy Expended field.
Where there are multiple RR-Interval values transmitted in the HEART RATE MEASUREMENT characteristic, the field uses the following format:
RR-Interval Value 0 (LSO...MSO), RR-Interval Value 1 (LSO...MSO), RR-Interval Value 2 (LSO...MSO), RR-Interval Value n (LSO...MSO).
Where the RR-Interval Value 0 is older than the RR-Interval Value 1.
RR-Interval Value 0 is transmitted first followed by the newer measurements.