I continue to change the variable, but seem to get this notice many times a day. 

Thank you. 

The subscription notification will show whenever the app is open on Android as UD Mobile needs to run a background service to ensure status values are updated as fast as possible and to properly handle resource cleanup when the app is closed. Resource cleanup may take longer than Android allows without a Background Service, so this notification may be present for a few dozen seconds after the app is closed even when set to 0 (zero). 

In your screen shot this variable is a negative number, so this notification may be shown forever as this instructs the app to never terminate the Background Service. 

The recommended setting is 1 (one minute).  This will keep the connection to your system alive for one minute, so if you return to the app within this time frame the app will not need to reconnect. Reconnecting to the system may delay status population by dozens of seconds depending on the seed of your internet connection (i.e. slow mobile internet).  During this one minute duration a notification will be shown so that you know the app is running.

 

Edit:

The notification is dependent on Android version.  Newer version do not show a notification for a background Service, they show as "Running Apps".  So this notification may not show on all devices.