PIR sensor MQTT string

I have several PIR sensors, the transmission being received by Sonoff RF bridge running Tasmota.

The received data looks like this:

{“RfReceived”:{“Sync”:9740,“Low”:310,“High”:960,“Data”:“74F63A”,“RfKey”:“None”}}

The “Data” element is the device detection code, but what are the Sync, Low and High elements referring to?