We charge per additional inch of length because of fabric usage, after the up to +2" uncharged additional length available on the Skater Items. 
Please note any length selected using this product will be the total length added, and any length selected on the product itself will be overridden by this additonal length being selected. Lengths selected on the item and on here are not added together (eg if you select +2" Length on the item's length option and +6" on this product, you will recieve +6" Length on your item)