TAB not change numbering

[dasza]

I have styles in my document. And I use write something, change styles, have numbering and use TAB to down number to 1.1 ect.

But sometimes I use style:
3.3 asjkajdkasjd
3.4 hajdhsadjshd
3.4.1 sdjahdjzfhs


3.4.2
3.5

but when I use TAB and want have 3.4.1 Word made 3.5!! But another place in document I use the same style and change to 3.4.1!!!!
I used this styles on different document and sometimes is perfect!! But when I want use styles on old documents and I want format to my new style numbering sometimes not work perfect.

Sorry for my English.