Installment Plans

Does anyone know how to do a setup like this?
much like how this site has it
https://dgachieve.com/repfh-int-order

” Sign up for our class ” $500 / 5 months
“Special Discount” 500 off

Order Summary
Item amount
Our Class $ 2500
discount $ – 500

(Complete my purchase button)

The page I need help with: [log in to see the link]