You bring up a good point, I noticed the same when I published some guidelines I had observed here:
http://forum.cyberlink.com/forum/posts/list/46629.page#post_box_241976 about what “SmartFit” appears to do. I'm unsure why PD uses a 24201MB as the shrink size as shown in your pick, lower left corner. Depends a little if they are true to the words and really talking MB as to my knowledge a 25GB BD has a capacity of 25025314816Bytes, 23866MB, so why PD shrinks to 24201MB is a little strange. Most other utilities I use for BD video creation use a margined capacity of right around 23000MB which makes sense, PD does not if they are using true MB nomenclature. If the 24201MB used by PD is true MB, then one's virtually always setting yourself up for potential failure. I’m guessing someone margined the BD capacity number not taking into account the real 1024 conversion. Other options also can reduce size, H.264 vs MPEG2, Dolby Digital vs LPCM but when you are overcapacity and use "SmartFit' these don't help as PD still reduces bitrate to an overcapacity situation. At times, the bitrate reduction algorithm behind “SmartFit” uses a bitrate that does actually fit the BD capacity periodically. Keep in mind, one's only talking a few percent change in bitrate between fitting and not fitting.
The way I get around it when I need to use "Smart Fit" type approach for BD is to preproduce my timeline to the proper bitrate with a custom profile to fit the stated BD size with proper margin and the codec of choice (MPEG2 or H.264). I then start a new project with this produced clip to use for creating a disc, behind the scene PD will use its "Smart Render" SVRT feature and not encode any of the timeline. I use the create a folder option and verify size of folder structure and then one can just use windows explore and drag and drop to burn to BD (guided verbiage here
http://forum.cyberlink.com/forum/posts/list/51482.page#post_box_270180 ). This custom BD bitrate was discussed at length here
http://forum.cyberlink.com/forum/posts/list/20867.page#post_box_117252 with a very detailed pdf showing exactly how to do it. Maybe this approach will work for you situation.
Jeff