Greetings all!

I need to edit a DOC file. I have Office 2013, but I believe it was created with Word 2010. But I have a problem with it.

The file has the following header structure:

1.
2.
3.
3.1
3.2
3.3
3.4
3.5
3.6
4.
4.1
4.2
4.3
4.4
5.
5.1
5.2

and so on...

But when I try to insert second level header anywhere outside 3., it does not assume the numbering of the particular subheader, but continues after 3.6. So if I try to add subheaders, it starts looking something like this:

1.
2.
3.
3.1
3.2
3.3
3.4
3.5
3.6
4.
4.1
4.2
3.6
3.7
4.3
4.4
5.
5.1
3.8
5.2

So basically it 'forgets' about other levels and continues the first subheader list.

Any ideas?