What is the number next to the opened file name in visual studio?

In visual studio, what does the number next to the file name represent? It is the exact same file.

Here is an example:

It started doing this a few weeks ago and I can't find any information about this. Is there a way to deactivate this feature?

What are the numbers next to files in VS code?

That is the number of linting errors and warnings currently in the file. To see the actual errors and their details, open the Problems panel, which by default is at the bottom part of the editor. (If it's not shown, open it by going to the menu View > Problems).

What is the thing after the in file name called?

After-the-dot-in-a-file-name, it is called extension.

What is the code to open all files in Visual Studio?

Features. This extension adds the option to the file explorer (and the command options, accessed with ctrl + shift + p, or cmd + shift + p on mac), to open all the files in the directory.

For me it's the window number instance whenever I open a new window for that file.