IQ2 sensor test graphs

I recently needed to review historical signal strength data for an S line smoke detector. I understand that strength in Db is the y axis, but what is the world is the x axis? I was expecting time, or perhaps time of day. I looks like numbers that are increasing. What am I missing here?

Of the top of my head, I think it’s “events” in where the sensor checks in with the panel for whatever reason.

Sensor communication is one way. There is no constant contact or polling from the panel, the sensor itself checks in with supervision signals.

The X axis is just a running tally of each signal from the sensor, labeled “Events.”