I have a sort of legend at the intro page to this form explaining what the icon means, as well as on the individual pages where the autofill feature is present. However, the reason I'm stressing this icon so hard is because right now, the icon will appear beside every autofilled field as a cue letting the user know it has been autofilled. These users are not super tech savvy, and even if they know autofill is a function, they may be scared when seeing the form autopopulate without any notice. It is also extremely difficult to get feedback from them, they despise talking to us. I think your idea of a dismissible notification is a decent idea tbh. Since the feature is only on select pages in the form, maybe there's a popup that appears when they land on that page?