In my firebase analytic event "first_open" shows 489 download till 7th july but in play store stats it shows 347 download till 7th july, i don't know why these no. is differ.
Definition of first_open is:-
When a user opens the app for the first time.
This event is not triggered when a user downloads the app onto a device, but instead when he or she first uses it. To see raw download numbers, look in Google Play Developer Console or in iTunesConnect.
But when user open my app for first time is 489 then at play store it should also be 489 or more, i don't know why this happen?
I have doubt if some user downloaded my app and open my app, firebase event first_open count increases by 1 what if a user uninstall and after some time reinstall then is it again increases the first_open of firebase analytic.
There are a number of reasons why first_open counts will differ from Google Play or App Store installs. You referred to one key distinction in our documentation. You also referred to a second one -- if a user installs, opens, uninstalls and opens the app again, that will count as one install in Play and two first_opens in Firebase.
The last important distinction is that when existing users migrate to the new version of your app which includes Firebase, they will log a first_open event. And so, even though they are not new users, they log a first_open. In the near future, we will change this behavior so that such events are filtered out of your first_open event report. However, those events will still be exported to BigQuery and will carry a flag that denotes that the first_open was due to a new Firebase integration.
In any case, once the majority of your users migrate to/past this first Firebase-integrated version of your app, this will be less of a factor in your reporting.
来源：https://stackoverflow.com/questions/38331910/how-event-first-open-in-firebase-analytic-count