Update comment per review

src/main.cpp

@@ -3084,8 +3084,10 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, CBlockIn
     }
 
     // Coinbase transaction must include an output sending 20% of
-    // the block reward to `FOUNDERS_REWARD_SCRIPT` until the first
+    // the block reward to a founders reward script, until the last founders
-    // subsidy halving block, with exception to the genesis block.
+    // reward block is reached, with exception of the genesis block.
+    // The last founders reward block is defined as the block just before the
+    // first subsidy halving block, which occurs at halving_interval + slow_start_shift
     if ((nHeight > 0) && (nHeight <= consensusParams.GetLastFoundersRewardBlockHeight())) {
         bool found = false;