Flat rate additional fee

Hi there,

Thanks for the free plugin. I have an issue.

I need to provide a flat rate of $35 for the first 20km. That works great by setting Max Distance: 20 & Minimum Cost: 35.
https://ibb.co/qdQTSSQ

The courier charges $2 per additional kilometer starting after the first 20 kilometers. I need to set that up using the plugin. Right now, the plugin multiplies the total distance by $2 after the first 20km.

The calculation I’m after when over 20km
————————————————–
Ex-
Total distance: 50km
Flat rate (first 20km): $35
Additional fee (after first 20km): 50km – 20km = 30km
30km * $2 = $60
Total fee = Additional fee (after first 20km) + Flat rate (first 20km)
$60 + 35 = $95

I hope this makes sense. Is this something which can be achieved by adding a discount?

Could you, please help me figure this out?

Cheers
Tasha