A matching bluetooth device is nearby.
If any of the parameters are specified the device must match that parameter, otherwise any device will match.
Standard/Low-Energy Devices: if you're only interested in a particular type of device, select only one of these to reduce power usage.
Non-Paired Devices: selecting this will use much more power and take longer to scan.
Toggle BT: if BT on the device is disabled, enable it for the period of the scan, probably around 5-15 seconds.
A seen device which is no longer visible for approximately two times the scan period is forgetten. This is to help prevent the profile bouncing on and off at the edge of the signal reception area.
The period for BT scanning is specified in Menu / Preferences / Monitor / BT Scan Time.