Agilent Technologies 1660A Series User Reference page 332

Statistics are based on the time between the X and O markers. Both
markers must be found before valid statistical information is
displayed.
In repetitive run mode, the display is updated each time a valid run
occurs until you select Stop. If you select Run after a Stop, the
statistics continue to update without loss of information.
In single run mode, each time you select Run, an additional valid run
will be added to the data and the statistics will be updated. This
process continues unless you change the placement of the X and O
markers between runs.
Statistics display
Statistics Display
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