Hi, so you have failed in one subject that you mentioned is extra. Okay so here are the two scenarios, first that it was the 6th subject or one in the 5. Just so you know that CBSE have 5 important subjects for example if you are a science student then (Physics, Chemistry, Maths or Biology, English) are the important ones. And some schools have 5th subject as a choice though it is mandatory to have a 5th subject but you have choices in them. Like you can have Hindi or physical as an optional. So failing in that can be an issue since you should be passed on 5 major subjects. Now if you have 6th subject i.e., extra then it is not much of an issue. Since your percentage depends of top 5 subjects. Repeating 12th is not the only solution you can fill out the compartment even if you have failed in one of your major subjects. So to sum up extra subjects doesn't create much of an issue but clearing up your failed subjects is always a good thing.