Why does my gross profit differ from expected on my first sale?

[Oneg]

Hey there, just got my first sale! 🙂

Customer ordered a product that costs $28 + shipment of $4.95 =  32.95

Gross profit  says 18.98, how come?

It seems that the customer used Shop Pay so taking 5.9% + $0.30 from 32.95 = 30.7

and then deducting the product cost so -9.02 = 21.68

The difference between 21.68 - 18.98 = 2.7 , where did the $2.7 go?

Just trying to understand how this works. Does Shopify take additional fee on top of the Shop Pay fee? 

Thank you 🙂