Managed Apps refers to the number of apps that your organisation can manage, or has the potential to manage, through appScatter.
The number of managed apps your organisation has is dependent on your choice of plan and any adjustments made to increase or decrease the number of managed apps.
An app becomes managed through appScatter once you have chosen to distribute it.
The number of app store you choose to distribute has no bearing on the number of managed apps taken from your pricing plan. You will have one managed app in appScatter whether choosing to distribute an app to just one app store or all supported app stores.
Once you have distributed an app and it becomes managed through appScatter, you can edit and submit your app for distribution as many times as you need to.