Shipping Classes for Woo-Commerce

Hi, here is my current shipping cost formula – ( 220 * [qty] ) for a shipping class. 220 is the base shipping cost for 1 product. If another product is added, i would like this formula to add an additional shipping cost of 150 to the total shipping cost. eg. 220+150=370. Same applies for every additional product greater than 1.

I have tried multiple formulas – here is a working formula i made in excel which works. IF QTY > 1, (NewBase * (QTY-1)) + Base, Base * QTY).

But this does not work with woo-commerce. please advise what i am doing wrong?

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