Why building an application in release mode marks warnings about “not found” files?

My app seems to be built fine in Debug mode, yet in Release mode I get 21 warnings about "no debug symbols file was found".

As I understood, debug mode uses some files that release mode doesn't need in order to run, I assume that the missing files are these ones. Maybe it's a problem with Xamarin or with VS?

Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.v7.AppCompat.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Java.Interop.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Arch.Core.Common.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Arch.Lifecycle.Common.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Arch.Lifecycle.Runtime.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Animated.Vector.Drawable.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Annotations.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Compat.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Core.UI.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Core.Utils.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Design.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Fragment.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Media.Compat.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Transition.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.v4.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.v7.RecyclerView.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.Android.Support.Vector.Drawable.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.GooglePlayServices.Base.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.GooglePlayServices.Basement.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.GooglePlayServices.Maps.dll but no debug symbols file was found. 0
Warning Directory obj\Release\81\android/assets contains Xamarin.GooglePlayServices.Tasks.dll but no debug symbols file was found. 0

1. What are those files? What those warnings mean?

2. What can I do about it?

3. Can those warnings cause any further damage?

I already tried:

1. Deleting those files from obj\Release\81\android/assets.

2. Cleaning the solution and the whole project.