what was special about this?
Judging by the description, it was only distributed to people who attended an event, probably one of those handshake/photo op/autograph events. Judging by the fact it also says it’s a DVD-R disc, they may have been burned right there at the event so that they didn’t make any more than they needed to, thus increasing its rarity. Burned discs also have a shorter data life than traditionally stamped discs (as I recall, it’s due to the fact that the adhesive in the disc eventually reverts to its “blank” status), so at some point these will no longer work.
As for its content, that’s up for debate. It probably at least contains a message from Saaya thanking the recipient for attending, but beyond that, who knows? Maybe some exclusive gravure, or exclusive behind-the-scenes photoshoot footage. The disc artwork may or may not provide a clue (DVD covers are not always indicative of video content; I know this firsthand