By default, the startup moment begins when the application starts (assuming the Embrace SDK start method is called in the onCreate method of the Application Class). The startup moment ends when the app's first activity goes to the foreground. Therefore, the duration of the startup moment is the time between app start and app in foreground.
To make any adjustments to the Startup Moment, refer to our technical documentation; https://embrace.io/docs/android/integration/session-reporting/#end-the-startup-moment.