how do build numbers exist without defining ios.buildNumber or android.versionCode?

Please provide the following:

  1. SDK Version: 36.0.0
  2. Platforms: iOS and Android

Question:
In app.json in my app ios.buildNumber and android.versionCode are not defined (they’re not present at all in the app.json file). However when Constants.nativeBuildVersion is outputted to the console “2.15.2.108043” is displayed for iOS and “134” is displayed for Android. How are these numbers being generated? (As an experiment I added them to app.json and doing so had no effect on the console output).