Shipping cost showing wrong

Hello

I have setup shipping cost for this https://wdnhorse.com/product/hoofprints-across-time-a-trail-ride-to-remember-hard-cover/ $8 and for this product https://wdnhorse.com/product/nez-perce-scarf/ $5 if i add both in cart shipping cost shows $5 instead $13 .

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