What you are seeing is called an inlay hint. When gray, it is simply a piece of ghost text showing you what type your variable is. This can change as you update your code. Personally I would not double click and insert them as I don't specify the data type a variable holds unless there is an outstanding reason to do so.
If they are annoying, you can disable them in the nimlang extension under the name of inlay hints. ps. I had to paste your image url into my browser in order to see it.
