press button that says decline challenge
Rematch??

I received a challenge for an online game from a member that says "rematch board 20". I do not recall playing against this member before. Why should I get a challenge for a rematch? I really don't have time to take on another game challenge at this time.
Please help me to understand this and what can I do if I do not want to accept this challenge?
If I said "rematch board 1" that means I complement you as a Board 1 player. But Board 20? That's absurd. I hope you are familiar with Team Matches where a team would place their best player (though not all the time) on Board 1. By far, I've only heard of Board 5.
I received a challenge for an online game from a member that says "rematch board 20". I do not recall playing against this member before. Why should I get a challenge for a rematch? I really don't have time to take on another game challenge at this time.
Please help me to understand this and what can I do if I do not want to accept this challenge?