//packages/contracts-bedrock/src/dispute/FaultDisputeGame.sol
  function move(
    Claim _disputed,
    uint256 _challengeIndex,
    Claim _claim,
    bool _isAttack
  ) public payable virtual {
...
|>      if (nextDuration.raw() > MAX_CLOCK_DURATION.raw() - CLOCK_EXTENSION.raw()) {
            // If the potential grandchild is an execution trace bisection root, double the clock extension.
            uint64 extensionPeriod =
                nextPositionDepth == SPLIT_DEPTH - 1 ? CLOCK_EXTENSION.raw() * 2 : CLOCK_EXTENSION.raw();
            nextDuration = Duration.wrap(MAX_CLOCK_DURATION.raw() - extensionPeriod);
        }
...
...
uint64 extensionPeriod;
if (nextPositionDepth != SPLIT_DEPTH - 1 && (nextDuration.raw() > MAX_CLOCK_DURATION.raw() - CLOCK_EXTENSION.raw())) {
     extensionPeriod = CLOCK_EXTENSION.raw();
} else if (nextPositionDepth == SPLIT_DEPTH - 1 && (nextDuration.raw() > MAX_CLOCK_DURATION.raw() - 2* CLOCK_EXTENSION.raw())) {
     extensionPeriod = CLOCK_EXTENSION.raw() * 2;
}
nextDuration = Duration.wrap(MAX_CLOCK_DURATION.raw() - extensionPeriod);
...
