We recently had a client who needed to shorten the default Magento Increment ID length from the default 9 characters (eg 100000000) to 6 characters. This can be accomplished by modifying the “increment_pad_length” in the “eav_entity_type” for whatever entity you’re wanting to modify.
Here is a screenshot of the resulting table:
If you’re wanting to change the number from which Magento starts counting orders/invoices/shipments, or wanting to change the prefix for those entities, check out this great post by Timothy at Elias: http://eliasinteractive.com/blog/magento-ecommerce-how-to-reset-all-test…