Formula
This allows you to set a filter consisting of a number of conditions, e.g., time controls, strength of the opponent, etc. Challenges that do not meet them will be automatically rejected.
Unrated/Rated/Ducats: request only unrated/rated games, including/excluding for Ducats.
No computers/centaurs: exclude pure computer games or computer assisted games (centaurs).
Elo: only games against players within the given Elo range.
Time/gain per move: rate of play – the time for all the moves and the íncrement per move.
Minimum rank: you can require that the opponent has a certain rank (guest, pawn, knight, etc.). These ranks are earned when you play on the server.
Minimum Ducats to override elo: If a weaker player offers you ducats for a game he/she can override your elo limit. Set your ducats price here.
Activate: You must click this on if you want the formula to be applied.
Reset: Clear everything, so that any challenge will be accepted.
Example
You want to play informal blitz games against opponents between 1500 and 1700 Elo.
Check "Unrated", uncheck "Rated"
Elo = 1500 - 1700
Time = 5 – 5
Gain per move = 0 – 0
Check "Activate"
If you get a direct challenge which match your formula they will appear in the challenge window. All others will be filtered out.