Why surcharge per transaction doesn't have % option?

We do not allow the percentage option for per-transaction fees. The illustration below should help you understand this more clearly.

Just assume if we allowed you to keep per transaction surcharge and you kept the per transaction surcharge as 5.00% and the ticket price is 100 $ and customer is purchasing 3 tickets it would come 15 $ as a Surcharge amount. If you keep per ticket surcharge as 5.00% and if a customer is buying one ticket at each transaction it would be $ 5 and for 3 tickets it would be $ 15. So it would remain same. That is the reason why we have not allowed the % option as a per transaction because it will not make any difference in terms of %. In per transaction surcharge you can decide a fixed amount and enter the amount accordingly.