Donation Amounts
At the top of the "Donation" page:

You can specify the default settings:
Frequency (One-time, Monthly, Yearly)
Amount for each frequency
The default frequency is the first tab users will see in the app.
The default amount is the preset amount users will see in the app.

In the example above, the Monthly frequency has been selected, and a default amount of $15. When app users open the donation view, they will land on the Monthly tab with a default preset amount of $15.
When a user toggles the frequency tab to One-Time or Yearly, they will land on the default amounts selected.

To change the Default Frequency, click on another tab:

To change default amounts, click on a different value:

Click the "Save" button to apply the changes.
The app will update dynamically with the new settings.