Thread:Jedm2311/@comment-5091911-20170715095320

"The Mystic Isles is a three part episode like Elena And The Secret Of Avalor so I'm guessing these are the production codes for the other two parts."

If there were three production codes it would have been noted on official websites, such as Disney Press, long ago. According to all sites that I know of it's production code number is just 405. Guesswork is not permitted on the articles, except in a discussion. 