I just "deciphered" this nice tip from Japan GR Blog. Let's say you need to delete multiple pictures in a row. The usual and commonly used technique is to go to the preview mode, switch to thumbnail mode (press zoom "down" button twice) and pressing the "Delete" button for each selected image. But this take time and a lot of Delete button clicks. However, there is also a faster way, which requires just one press of Delete button!
Turn the camera to thumbnail preview mode.
Select a photo where you would like to start with deleting.
Press Adj. button and then Delete button - selection is switched to a special multi selection mode.
Now simply go left/right for adding one new image into multiselection stack (or up/down for adding rows).
Now you can press OK to delete all selected images.
To discard multiselection (and Delete operation) press the Disp. button.