When there is a seventh character extension in some categories it is used to describe what?

With the presence of seventh character extensions in some categories, it is used in ICD-10-CM. It is being used specifically in organizing visits. Aside from the visits, it is also used in finding out the problems that could be encountered. From how it is named, it is always required for the characters must be in seventh position. This is also the reason as to why it is named after it.