Using same corner radius setting for both outer and inner rounded rectangles will create a “lump” corner like an eaten mice in snake’s stomach.
Radius number should always be lower for inner box. In measurement example picture above, I used 14 px for outer box, 8 px for inner box to create a perfect size border all across the corners.
Photoshop’s Rounded Rectangle Tool Setting.
Image below is an example of widget box my brother designed with incorrect radius setting:
While average Joe will not notice this, it’s something that all graphic designers should know. It will make your work look more professional and accurate.