Work breakdown structure update

One of my project managers used the auto-calculate WBS, but he is having an issue when he exports to excel. His 4th section has 20 tasks in it so it starts 4.1, 4.2......4.19, 4.20. But when 4.2 and 4.20 export to excel they both write out as 4.2. He can reformat once in excel, but our projects have hundreds of tasks so the effort is too much. Suggestion to add another decimal to WBS so it starts with 4.01, 4.02, etc.