if i'm not wrong, it shows the usage of data WLAN/mobile of each app.

But what if we change smart to allow etc?

i think the smart is for use the data only when is needed when allow it uses it continuously.

Yes... i agree..

Apps continuously connect to the service you're using it for, or to download ads, or jusreto synchronise with your Google account and Google Play Services. To prevent this from using more battery and data Flyme automatically manages which app sends how much data. If smart background data connection breaks the ability of some apps, then you can always change it to allow background data connection. This feature is mildly similar to the battery saver in stock Android 7 which restricts data usage when battery saver is turned on.

Thank