Upadate size always same as Real App size on Google Play Store

My App was build Using React Native.Actual size of my App was 27 MB on Google Play Store.If any small change was done in my app user should Update his App with full size(27 MB) from google Play Store.So any one can Help that how to reduce full size update and give only those part of update which I am giving from previous App.

I went through below blogs and links:

https://medium.com/androiddevelopers/tracking-app-update-sizes-1a1f57634f7b

https://android-developers.googleblog.com/2016/07/improvements-for-smaller-app-downloads.html

Reduce APK Size using Patch and Update on Google Play Store

and I also know that I don't need to download BS Diff or the patching code. Play will do this automatically.I also wanted to Know thus Google Play will do patching Depends on Popularity.There is 1000+ downloads of My App.Still app showing same size of Update.