My outline heading got a problem after I installed a new office. How can I delete "2." before "2.1" in my numbering system. Thanks!


original outline:
Chapter 1
1.1
1.2
1.3
1.3.1

Chapter 2
2.1
2.2
2.3

New outline after I installed a new office
Chapter 1
1.1
1.2
1.3
1.3.1

Chapter 2
2.
2.1
2.2
2.3

However, I cannot delete "2.", otherwise the outline will become
Chapter 2
1.4
1.5
1.6