Hi @Amarnadh,
If the campaign code is 99999, the next incremental value will be 100000 rather than 00001. After 100000, the next campaign codes will be 100001, 100002, 100003...
The other values in the sequence table behave in this same way.
If you want it to behave differently (go back to 00001, you'll have to do it manually (edit the table) or programmatically (set the value).
Hope that helps you.
Cheers,
Damo