compiledSdkVersion==> which version of SDK should compile your code to bytecode(it uses in development environment) point: it's better use last version of SDK.
minSdkVersion==> these item uses for installation of APK(it uses in production environment). For example:
if(client-sdk-version < min-sdk-versoin )
client-can-not-install-apk;
else
client-can-install-apk;