Account Base Code recorded twice

Hi,

I have an issue with this in Tax management. Take a simple example. I import a product, named A. Product A will be taxed with 2 kinds of taxes, import tax and VAT tax. Import tax is based on import price, VAT tax is the same.
I named Account Base Code for product A is 'import product'. Then setup 2 Account Tax Codes, '5% imported', '10% VAT'.

Now, I make a purchase invoice for product A, including 2 kinds of taxes. Then approve this invoice. For ex, price of product A is 1000. Looking at chart of tax, I see that value of 'import product' account is 2000. This is meaningless. I think so. Value of account '5% imported' and '10% VAT' is right, 50 and 100.

Thanks.