The Quantity Committed appears higher than Quantity On Hand is because it already includes the Quantity Picked. This also happens when there are frequent changes made on the Accounting Preference: Fulfill Based on Commitment per Audit Trail of Preferences via Setup > Accounting > Accounting Preferences > More (located at upper right side of the page) > Audit Trail. When the Accounting Preference: Fulfill Based on Commitment is set to Allow Uncommitted, and a Sales Order, from which the quantity is on back order, is fulfilled to Picked Status, the Quantity Committed increases while the Quantity on Hand remains.