The 'Price Adjustment Value' comes from the value adjustments of the products in the 'Stock Location'. If you make any 'Unit Value' adjustments to one of your products in Inventory, this will show as a price adjustment value in the Reconciliation report. This may be due to a price discrepancy, or perhaps the product ordered was invoiced per carton instead of per unit.
The 'Price Adjustment Value' shows the total difference of unit price before the adjustments and after. An example would be if you have 10 units of a product priced at $50, and you change the value of that product to $48 then the 'Price Adjustment Value' would be -$20 as the price changed by $2 across a quantity of 10 units (2 x 10).