Cost decrease does not affect quantity.

and location details costing will not be updated until DayEnd.

I mentioned about cost not quantity.

After Dayend also not updating the cost.

Double check your work. This is a simple process that works. Or call your Sage consultant to take a look.

What does this mean then: "In ICILOC table i saw Qtyonhand is 11 and Qtyshnocst 3 and Qtyavailable is 8."?

The first sentence you mention cost. The third you are referring to quantity. What is the issue you are having?
What is the correct figure for what field? What field (or screen or report) is showing the incorrect value? and what is the incorrect value?

The incorrect value is Cost.We adjusted the cost (Cost decrease) only. Inventory movement and Stock transaction report are correct. Its showing the average cost as 325.567 means correct figure. But in location details the average cost is 353.598 means wrong figure.

The only value to consider is what you see in IC location details, the others are just reports and the movement report is notoriously bad. Look in the ICILOC table - average cost is calculated by TOTALCOST / QTYONHAND provided that all transactions have been processed by IC dayend. If not then average = TOTALCOST / (QTYONHAND - QTYSHNOCST + QTYRENOCST - QTYADNOCST)