HP 54710A User's Reference Manual page 296

Trigger Menu
Mode
Figure 18-7 shows a delay-by-events timing diagram. You may notice that the
arming event is channel 1, and the trigger event is channel 2. By changing
the number of events, you can consecutively look at pulses in a pulse burst
without the effects of jitter. The first event to satisfy the trigger conditions
after the number of events are counted triggers the oscilloscope.
Figure 18-7
Example of a when a trigger occurs on a delay by events timing diagram
18–17