Tested on SuperCard SD
AYAEdemo = Big Brain Academy Demo
ATDEdart = Clubhouse Games (Darts Demo)
ATDEturn = Clubhouse Games (Turncoat Demo)
ATJEclip = 0b file - SFC or STTA vid
AMQEdemo = 0b file - Presume this is Mario vs Donkey Kong
ANDEdemo = Brain Age demo
ANPEdemo = Danny Phantom demo
AOSEdemo = Elite Beat Agents - No trim rom, no restart patch
ASFEclip = 0b file - SFC or STTA vid
ASUEclip = Spectrobes vid (Must enable patch cart access) - As far as I can tell, not a single second of actual gameplay footage - For shame
Use the Supercard homebrew converter available at
http://www.pat.hi-ho.ne.jp/sata68/nds.shtml#scconvI've tested and confirmed it works with all the video clips, Mario vs DK, and EBA (which wasn't working with your method)
I normally use it for homebrew, but it seems to work with these demos as well
(note: it will create a .SC file, just directly copy and paste it to your memory stick)