Auto-number Headings Always Restart at 1

Hi,

I need to have numbered headings, for example:

1.0 Heading 1

   1.1 Heading 2

          1.1.1 Heading 3

2.0 Heading 1

    2.1 Heading 2

           2.1.1 Heading 3

I need to apply this new style to all the headings currently in use.  I edited an existing heading style by selecting the autonumber button on the styles box.  I created the number to be:  <x> (for heading 1) and <x>.<x> (for heading 2) and so on.  I also selected Decimal numbering.

I applied the updated styles and everything looks perfect except I can't figure out how to get subsequent files to continue numbering.  The first heading in a new file always begins with 1, regardless of its heading level.

I'm familiar with numbered lists and regularly use the "restart numbering" feature. I was looking for some option like that but I must be missing something because I'm trying to make a numbered paragaph style.  Out of desperation, I even right-clicked on the numbered heading and selected List Style, only to find "restart numbering" was NOT selected.   

I know this question has been asked before (I searched) but I wasn't able to find the answer.

thank you so much!

Robohelp 11.0.4.291, Webhelp

On a side note: These files were imported into RH from Frame and contained Frame numbered headings.  The numbered headings converted to regular text because I had to apply an existing css to the files for continuity across publications.  It's too late to go back and re-import the files now - I've done way to much messy work/clean-up on the converted files!