Calculations not right, or I setup wrong

I’m not sure if I am misunderstanding something, or if I have my calculations wrong. I’m trying to setup extra fees for Stripe – 1.7% surcharge + $0.30. These are my settings:

https://www.dropbox.com/scl/fi/uckmpt4oy16j2n92l8tb5/settings.jpg?rlkey=etk403ogmw8thuypqif5ulxt5&dl=0

But I’m getting strange results with the surcharge for example on this order I would be expecting the surcharge to be about $0.86 or $0.87 with tax (1.7% of subtotal + $0.30 + $0.10 tax) – but its much higher around 4.2%!!

https://www.dropbox.com/scl/fi/rtt3996iyivmoqqwhw41t/calculation.png?rlkey=kuvz3iyqp0vmx5mm9kzayqw4l&dl=0

I don’t have any other settings in place, no Global fee, nothing on any other Payment processor.

Have I got the settings wrong?

Thanks