Pro Rata for all payment periods
At the moment, Pro Rata says that its applied only on monthly and yearly periods (https://imgur.com/a/s4flGc3).
When a service with a different period is selected, it will be pro rated to the next month, which is fine in some cases, but for services that are really cheap, this can make them quite unprofitable in that first month.
I got a 4.68 GBP/year service pro rated to the next month for 0.35 GBP, which all goes to payment processing fees... (https://imgur.com/a/9hQplH7)
It would be nice if the services can be pro rated based on their selected payment period.