Once in a while my sequence numbers for items on a page end up being consecutive. Adding an item after that means editing the items and changing the sequence number, not a very pleasant job. Like in the following situation:
If I want to add an item between P7_CUST_LAST_NAME and P7_CUST_STREET_ADDRESS1, I have to edit the sequence of both P7_CUST_STREET_ADDRESS1 and P7_CUST_STREET_ADDRESS2 before I can add this new item.
As you can see the sequence numbers have been cleaned up with increments of 10! This example shows the clean up for items on a page, but this feature cleans up all page components (regions, buttons and processes etc.).