If you accidentally select an answer, you can easily Reset your selection in both the desktop version of AMBOSS and the mobile apps. By resetting, your initial answer choice will not be reflected to your statistics. Here’s how you can do so:
After selecting an answer in the desktop version of AMBOSS, click on Reset Question at the bottom right corner of the question window.
Open the Options window (look for three small vertical dots in the bottom right corner), then select Undo.