Since many smartphone users are sensitive to the amount of data they use, especially if they are not on Wi-Fi, Google Play is investing in improvements to reduce the data that needs to be transferred for app installs and updates.
Now Google has thus worked on reducing the data required for installs and updates, also clarifying data cost to users in the process. The new algorithm does this by compressing the size of patches.
The new Delta Bsdiff Algorithm will reduce the data required to install the app update. For approximately 98 percent of app updates from the Play Store, only changes (deltas) to APK files are downloaded and merged with the existing files, reducing the size of updates.
So now you will get reduced app update size on Google Play Store.