This is presumably just the withholding tax of the country of domicile of those stocks. You need to pay Swiss taxes on these dividends in any case (although depending on the country, you may get a tax credit via DA-1 to compensate for the withholding taxes), so it’s not really post tax.
I assume that line in the declaration is the only one with regards to that broker account, i.e., there aren’t additional lines in the declaration for the individual stocks you hold there.
In that case, it certainly doesn’t seem completely correct, however, if the declared tax value is the sum of cash and all stocks at that broker and the sum of gross dividends of all stocks are declared as income on the same line, the totals would be correct. You have to attach the broker statement to the tax declaration but the only mistake would be that it’s categorized as bank account instead of depot or similar (I don’t know what categories are available in GE), and that doesn’t really affect anything.
However, if the dividends were not declared at all, that would be an incomplete tax declaration.
The official, certainly correct way is to declare each stock separately (and only the cash part of the broker as a bank account). Maybe this helps you: Filing Taxes in Geneva - a couple of questions