Ordered lists are part of Markdown just as they are part of HTML. And just like HTML, you don't need to number the individual list items properly, even though the syntax makes it seem like you do. This is especially useful when you have a very long list and need to move things around or insert items in the middle.
1. First item
2. Second item
3. Third item- First item
- Second item
- Third item
1. First item
1. Second item
1. Third item- First item
- Second item
- Third item
Will automatically number the items starting from the first item's number.
1000. First item
0143. Second item
51. Third item- First item
- Second item
- Third item