There may come a time when you want to start an ordered list on a different letter than the default.

Example using default :

1. first item
2. second item
3. third item
4. fourth item

And by using a reference point for the list to start at :

7. first item
8. second item
9. third item
10. fourth item

The 7 in the example above represents the 7th letter of the alphabet, thus the second list starts at g.