What does this mean? (Sleepyhead)

What do those red squares mean next to my apnea events?

Pressure pulses...little puffs of pressure that the machine uses to help it decide if what it is sensing is either central or obstructive in nature....open or closed airway.
May or may not be seen with a flagged event or may just be random test but event doesn't meet criteria for a scored event.

Alright thanks for the explanation doc