change reducibleChallengePeriod logic

Author: KeaneHh

src/core/FinalityRelayerManager.sol

@@ -131,8 +131,8 @@ contract FinalityRelayerManager is OwnableUpgradeable, FinalityRelayerManagerSto
 
     // ==============================internal function====================================
     function reducibleChallengePeriod(uint256 votedManta, uint256 votedBitcoin) internal view returns(uint256) {
-        uint256 reduciblePeriod =  (votedManta * MANTA_REDUCE_PERIOD) / TARGET_MANTA + (votedBitcoin * BITCOIN_REDUCE_PERIOD) / TARGET_BITCOIN;
-        if ((TOTAL_CHALLENGE_PERIOD - reduciblePeriod) < MIN_CHALLENGE_PERIOD) {
+        uint256 reduciblePeriod =  TOTAL_CHALLENGE_PERIOD - ((votedManta * MANTA_REDUCE_PERIOD) / TARGET_MANTA + (votedBitcoin * BITCOIN_REDUCE_PERIOD) / TARGET_BITCOIN);
+        if (reduciblePeriod < MIN_CHALLENGE_PERIOD) {
             return MIN_CHALLENGE_PERIOD;
         }
         return reduciblePeriod;