Top 25 Challenges must be made thru the lobby. When you are ranked in the Top 25, ask in the lobby for challengers, then state your rank and that of the highest available challenger 3 times, then accept the highest available challenger. If you are ranked in the Top 25 and challenge another player, but a better ranked player wins that challenge - you must then open up your rank for challenges. By challenging for an Up game you are showing that you are available to play. After that challenge is completed, you are then free to challenge for another Up game.

For Example:

PlayerA: Rung #5 Open for challenges
ChallengerA: Rung #35 challenges #5
ChallengerB: Rung #22 challenges #5
ChallengerC: Rung #16 challenges #5
ChallengerD: Rung #9 challenges #5
PlayerA: 5 v 9 going once
PlayerA: 5 v 9 going 2x
PlayerA: 5 v 9 challenge on, come to table X

By making challenges, ChallengerA, ChallengerB & ChallengerC have declared they are also available for challenges, and have to accept challenges themselves.