L3Harris narda PMM EP-600 User Manual page 66

It shows the time interval (in seconds) between subsequent readings.
5.5.4 Reading Rate
Setting resolution of 0.1 s.
setting
Press the enter key to enter the set frequency value.
The setting displayed at the first run is the default; the last setting will
be displayed then.
The minimum time interval between readings is in function of the filter
setting. The table Filter (Settings/Filter) show the minimum reading
rate allowed.
The max. time interval between readings is of 30 s regardless of the
filter setting.
Entering a reading rate not allowed will cause a warning message to
appear:
5-12 WinEP600 and SetAddEP600 operating instructions