@Akervin 

"This shows me past inventory adjustments but does not allow me to adjust them all at once, I still have to click each one individually."

Is there a reason you aren't making a batch inventory adjustment?  There's no need to adjust each item individually.  Go to Settings > Products and services.  Click the funnel (filter) and under 'Type', check the Inventory box.  Then (I forgot this step in my last post), click the box to the left of 'Name' to select all items.  When you do that, you will see a 'Batch actions' drop-down appear on the right.  Click 'Adjust quantity' and you can adjust all inventory items at once.