[DOCS] RETAIN option clarification only for white/black-list (#1937)

docs/use/ble.md

@@ -137,6 +137,8 @@ to enable white/black list back
 ::: tip
 So as to keep your white/black list persistent you can publish it with the retain option of MQTT (-r with mosquitto_pub or retain check box of MQTT Explorer)
 `mosquitto_pub -r -t home/OpenMQTTGateway/commands/MQTTtoBT/config -m '{"white-list":["01:23:14:55:16:15","4C:65:77:88:9C:79","4C:65:A6:66:3C:79"]}'`
+
+**NOTE**: Only when sending a white/black list should the retain option be set. All other commands to any OpenMQTTGateway gateway **must not** have the retain option set. To persist such other command settings, read [the following section](https://docs.openmqttgateway.com/use/ble.html#store-ble-configuration-into-the-gateway)
 :::
 
 ## Setting the time between BLE scans and force a scan (available with HA discovery)