Banner image in Dexterity Theme

Anyone using Dexterity in RW 7.02?

These instructions have the line:

2. Open your page inspector and locate the Banner Area and the Number of Slides options.

So I set the Banner for the Theme to ‘Static Image or Third Party Plugin’

My image is in %resources%, banner_1.jpg

Yet in Portable Project it fails to display; the source has changed the image to banner_12x.jpg

No reference to any version of that file in the Sidebar gets the image to display.

Anyone figured this out, please?