Extracted an Apk using APKTool getting the manifest.xml like this,
platformBuildVersionCode overrides and takes precedence over android:targetSdkVersion in the merged AndroidManifest. This is evidenced in the following android git commit:
https://android.googlesource.com/platform/frameworks/base/+/ad2d07d
platformBuildVersionCode is added by a compiler, and means a version of targetSDK
platformBuildVersionName is a readable version name of targetSDK version.
After a long analysis,
i got solution,platformBuildVersionCode is targetSDKVersion and platformBuildVersionName is version name of targetSDK(like Android 6.0) which are mentioned in build.gradle.