Here's my best guess based on the fair play policy. I think that 15 to 20 seconds for the first move is not widely known.
Tips to Avoid Aborting Games!
Aborting games too often will temporarily suspend your ability to abort games. This means that if you cannot play, you will have no choice but to resign (or risk further sanctions described above, by abandoning your game or disconnecting). If you have to abort, then do so of course, but whenever possible, use the features available to minimize your need to abort chess games!
Do not Abort games if your opponent will not move at the beginning of a game: The server will do it for you!
On his or her turn, each player has 15-20 seconds to make their first move. If this does not happen, the game will be automatically aborted. This has a negative effect on the Fair-Play record of the player failing to move. (But if you hit Abort, it affects your record! It's best to be patient for a few seconds.)
When I play Live Chess, many games are aborted by the server. Why it is happening?