Sometimes, it may be the case that your AirVisual Pro's screen may update its readings at a slightly different rate than to your AirVisual app.
Your device will take measurements at different intervals, depending on its sensor mode. See more about the different sensor modes here:
In the standard 'Default' sensor mode, the Pro will take a measurement every 5 seconds when actively being used (this means when buttons are being pressed). After 10 minutes of inactivity, when the screen is still on, the Pro will change to take measurements every 5 minutes. Meanwhile, at any time when the screen is off, the Pro will take measurements every 15 minutes. These new measurements will be displayed on-screen, whenever the Pro's screen is on.
If the device is connected to internet, its readings will update on the app once every 5 minutes. What is then displayed on the app is shown as the average value for the past 5 minutes. Therefore, if your monitor screen is showing updated measurements every 5-10 seconds, but your app does not reflect these immediately, this is the reason why.