Although you can't send any after fifty this is just a measure taken by nintendo to control traffic in the first few weeks. This limit has already been lifted in Japan and it will soon be lifted in the USA. You can only send one pokemon a day from the dream world, the reason it allows you to hold 10 at a time on the board is because if you don't send the pokemon down via the entralink on one day it will still be the next day. You can do this up to 10 days before you actually have to transfer them, however you get more dream points if you transfer every day instead of waiting. I hope this helped!