Appearance and disappearance of a block with a counter - JavaScript?

Question

JavaScript

Good afternoon, tell me who is familiar with how to implement the following functionality in javascript or jquery. There is a landing, when scrolling to certain sections, a pop-up message should appear and disappear, while on the landing there is the number 15 and with the appearance of each window it should decrease by 1. For example, the 1st message appeared - it became 14, the second - it became 13.

Answer 1

Something like this? (the code is dirty, but you get the idea)
https://jsfiddle.net/olegcvetkov76/re5gmz50/