How to Fix This Feed is Valid, Interoperability Range of Feed Reader

Sometimes, even our RSS feed blog is valid, but when you check on feed validator like Feed validator, you receive the following message:

"This feed is valid, but interoperability with the widest range of feed readers could be improved by implementing the following recommendations."(check these image below)

Fix Error Feed

1. Go to Feedburner
2. Choose your feed
3. Click Optimize
4. Activate Convert Format Burner and Summary Burner
5. Done

This is result my RSS feed


Note :
- This is for RSS feed from Feedburner service. I dont know it will work or not for other RSS feed services