You may notice a difference of AQI between 2 phones using the same AirVisual app and the same station. The discrepancy comes from using a different AQI system. Phones with Chinese language display the Chinese AQI by default while all the other phones use the US AQI by default.
To display the same AQI standard, just go to the app settings > User Preferences > AQI Index > select the same AQI system.