When entering the Opening Balance, you also enter the stock value.
With the step mentioned in fawiki to add stock, the stock value is added again. So you have the double value in FA. Step 8 in fawiki is needed to correct for this double value.

I only understand the basics of accounting. If I ask stupid things, please forgive me!

I follow the steps mentioned in fawiki (https://frontaccounting.com/fawiki/index.php?n=Main.OpeningBalances) under "Advanced". After step 7, my balance sheet looks ok.(Total Liabilities and Equities has correct amount). Also the GL Stock has the correct ammount in debet. The GL "Inventory Adjustment" has the same ammount in credit.

I think, this is ok.

Question: Why is step 8 in fawiki needed and what does it do?