Adjusting the inventory quantity in and of itself doesn't change quantities related to active listings.
Here's a synopsis of what happens.
When you add an inventory item or adjust its quantity, that doesn't itself affect your listings e.g. it doesn't affect what has already been posted and is considered "active".
When you create and schedule a listing for an inventory item, auantity is removed (decremented) from inventory. That item is now 'gone' from inventory and nothing further happens to the inventory quantity of that item *unless* the schedule for the listing is canceled or the the item's listing posts but does not sell; in both cases the quantity is put back into inventory.
By the way, if you import a listing from your active listing page back into Auctiva, those items won't automatically show up as active inventory quantities since those items may not have been posted from Auctiva and weren't in inventory. The only link between inventory and a listing is when you first have the item on hand in inventory and then schedule it to list it through Auctiva.
I hope this helps.