GST calculation is not working properly in woocommerce

I need to show price in cart with GST amount. GST rate is 18%. But the cart shows the GST amount as 1.80Rs always. I need to calculate GST amount based on total cart price.

In this example the GST amount should be 7040.592Rs. But it showing only 1.80 which means it is calculated like 18/100, instead of total * 18 / 100
My settings are

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