The "Preview" block displays the final result of your counter and its "Bandwidth" which affects the download speed. There are also additional settings:
"Transparent" - makes the background transparent.
"Disable Days" - removes the "days" segment from the counter.
"Fixed Cube" - sets the same (large) width for all segments. Made to set the same distance between all segments.
"Reverse Label" - positions the labels to the opposite position from the digits of the counter.