click this link for the original annoucement with instructions.
http://gtm.steamproxy.vip/groups/TFRafflingTrading#announcements/detail/120794580774837469

Invite 60people for 1slot
maximum of 3 slots
no limit on joiners
welcome to invite more than 180 people but 180down is all you will be accounted for.

Post evidence of your invites in the comments.