As a safety measure, you are prevented from making entries to the inventory account except through the inventory system.  This is because your inventory account in the general ledger should always be the total of all of your individual inventory items at cost.

I suggest talking to the accountant who gave you the AJE for more instructions.  Does the accountant want you to adjust one or more specific inventory items?  Does the accountant want you to fix a mismatch between your inventory total (from the inventory system) and your inventory account (from the general ledger)?