Apple Pay Moneris Recurring Payments with top ups

Through our app consumers are able to purchase fuel. We are trying to implement a subscription top-up model where the customers get charged the difference of what they have on their wallet and a maximum they defined in a subscription. For example if the user subscribes to have 100$ on their wallet, and they currently have 50$ we would charge them 50$ (when their subscription renews) and add that to their wallet so they can purchase fuel.

We checked out the Moneris Apple Pay SDK here and it mentions how to create recurring payments but is it possible to have variable amount subscriptions as described above.

To summarize is it possible to:

1. Create variable amount subscription through Moneris.
2. Get a token from Moneris by providing an apple pay token which allows us to manage the subscription charging on our end.