Reply To: Numbers don't restart after ANY previous level—only the immediately previous one

1. — list1
1.1 — list2
1.2 — list2
1.3 — list2
2. — list1
2.3.1 — list3
2.1 — list2

In your case, I think you are applying the styles as mentioned above. You are applying List3 style just after the List1 resulting in 2.3.1.

Level 3 needs a preceding list, in your case you have not applied List2, ideally it should be like this:

1. — list1
1.1 — list2
1.2 — list2
1.3 — list2
2. — list1
2.1 — list2
2.1.1 — list3

However, when List looks backward, it didn’t find 2.1, hence it took the list2 from 1.3, therefore, 3 is carried forward resulting in 2.3.1.

If you apply List3 on second line i.e. 1.1, it will become 1.0.1 as there is no previous list before 1 and 2.3.1 will become 2.2.1

It shows that the order should be consistent i.e. 1, 1.1, 1.2, 1.3, 2, 2.1 2.1.1
OR
List1, List2, List2, List2, List1, List2, List3.

You have to go section by section, you can’t skip a section in between.

Just go through the url once again:
https://blogs.adobe.com/indesigndocs/2009/04/numbered_lists_part_ii_multile.html

I hope you got my point.