attempting to add an inventoryAdjustment transaction but i'm stumped by this error:

code => 'INSUFFICIENT_PERMISSION'
					message => 'You do not have permissions to set a value for element inventoryassignment.quantity due to one of the following reasons: 1) The field is read-only; 2) An associated feature is disabled; 3) The field is available either when a record is created or updated, but not in both cases.'
					afterSubmitFailed => null
					type => 'ERROR'