Unfortunately the screen you're seeing cannot be edited. (Not even sure why that screen is shown but, it has happened to others too.) The Donation item button code that you can create online allows you to configure it for a fixed amount or let the Donor enter any amount - that's about it for options. Seems once you create the code, sometimes you get the Checkout Screen you expect and sometimes you get a screen with the fixed amounts - go figure. (At least from what I've seen and tinkered with.) Seems that one work around is manually create the Donation code, doing so also allows more flexibility whereas you can setup Radio Buttons for selecting different amounts and also include a text box for entering any amount - the one thing I've noticed when you use this method is that there's no option for a recurring amount however, there's also a work around for that by using the Subscription button code. You may want to visit the Merchant Support Community as there are other developers and PayPal Techs who may be able to help.
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