I’m not sure this is the right place for this question - but the answer is, from Incontrol you have Uptime and Online time :
Uptime is the amount of time the device has been powered on (so the amount of time since the last reboot)
Online time is the amount of time the device has been connected to InControl
If you have a single WAN connection (cellular on a BR1 Mini, for instance), this could stop working for a period of time (data usage, mast issue, poor signal, etc) - this would cause the device to show as Off-Line. Once the connection is re-established, the device shows On-Line and the amount of time it has been on-line. However, if this event was not caused by a power cycle, then the uptime and online time will be different.
Hope this helps,
Steve