From the owners manual:
"The Smart Fit option automatically adjusts the bit rate to the best quality video file that fits exactly to the capacity of the disc you are using."

Well then, how come I have Smart Fit set as the Video Quality and 4849 / 4700 MB is down at the bottom of the main Create Disc page and I get the following warning when trying to burn?:

"The detected disk size is (4699MB) is smaller than the estimated production size (4849). Are you sure the disk is large enough to accommodate your production? Press OK to continue burning."

Not too smart is it.