when you chose Epoch as your preferred biller, you are automatically switched to the 100 credits bundle which contains this membership offer.
I have not experienced the Credit amount changing
when selecting Paypal.
Your Credit amount Choice takes Place Before you proceed to Epoch and switch to Paypal,
and that is encoded in the URL along with your account information.
I've just tested with the 25, 250, and 500 credit options.
they all remained at 25, 250, or 500 after selecting paypal
What does Happen, is the Check boxes to OPT out
when you have to 100 credit package selected, are no longer displayed when you select paypal.
But I don't think Paypal can be Auto Rebuilled. I think with Paypal you need to setup a subscription
through Paypal.
So the removal of the check boxes, is because they can't auto rebill your paypal account without you setting up a paypal subscription.
And you would see that on the Paypal Payment Screen.
That you are agreeing to a reoccurring payment.
Also, in your Paypal Dashboard
you can manage your Automatic Payments, and switch them off.