@Ryad-Arlan ,
Search/replace (regex) does not know how to count. So it cannot increment your replacement, and it cannot count how many replacements it has done.
To do that, you need a programming language. If you use a plugin like PythonScript, you can leverage the full power of the Python language and give it the access to the contents of the Notepad++ editor window. If you’re willing to go that route, you can search the forum for add_1 and find a lot of examples for the “add_1” style of pythonscript search-and-increment-replace. For stopping after 20 instances, you can look at the optional final argument of the editor.rereplace(search, replace[, flags[, startPosition[, endPosition[, maxCount]]]]) method.
if you have trouble customizing what you’ve seen elsewhere for your specific situation, show us what you’ve tried, and we might be able to point out where it’s gone wrong.