Visual Studio 2013: What do the number suffixes in the file tabs mean?

Question

I just upgraded from VS2010 to VS2013 and now once in a while I will see a number in some of my tabs:

I searched Google, MSDN and here with no avail to an answer.

Any idea what these numbers mean?

Answer 1

The numbers indicate different views of a file. You can open additional views from the main VS menu Window - New Window.

As for why they appear by themselves for .aspx files, it could be a bug in VS. I also heard about this problem from a colleague.