Transaction Charge Variation on Rave Checkout Page

Rave
1

I noticed a transaction of 10,000 naira with the transaction charge (1.4%) applied results to 10,140 naira on Rave page which is 1.4% of 10,000 naira but a transaction of 190,000 naira with the transaction charge (1.4%) applied results to 192,000 on Rave page which is not 1.4% of 192,000 naira.

Why the difference in the transaction rate?
Is there a real-time API to consume for charges since it varies?

2

I resolved this by getting the transaction fee before checking out. Transactions