f improve comment clarity and correctness

Author: TheBlueMatt

lightning/src/routing/network_graph.rs

@@ -374,13 +374,18 @@ impl<C: Deref , L: Deref > RoutingMessageHandler for NetGraphMsgHandler<C, L> wh
 		let mut pending_events = self.pending_events.lock().unwrap();
 		let batch_count = batches.len();
 		for (batch_index, batch) in batches.into_iter().enumerate() {
-			// Per spec, the initial first_blocknum needs to be <= the query's first_blocknum and subsequent
-			// must be >= the prior reply. We'll simplify this by using the query's first_blocknum since its
-			// still spec compliant and sequence completion is now explicit.
+			// Per spec, the initial `first_blocknum` needs to be <= the query's `first_blocknum`
+			// and subsequent `first_blocknum`s must be >= the prior reply's `first_blocknum`.
+			// We'll simplify this by using the query's first_blocknum since its still spec
+			// compliant and sequence completion is now explicit.
 			let first_blocknum = msg.first_blocknum;
 
-			// Per spec, the last end_block needs to be >= the query's end_blocknum. Last
-			// reply calculates difference between the query's end_blocknum and the start of the reply.
+			// Per spec, the last end_block needs to be >= the query's end_blocknum.
+			// Each message carries the number of blocks its contents fit in, though there is no
+			// requirement that we use exactly the number of blocks its contents are from.
+			//
+			// For the last reply, we calculate the difference between the query's end_blocknum and
+			// the start of the reply.
 			// Overflow safe since end_blocknum must be >= msg.first_block_num.
 			let number_of_blocks = if batch_index == batch_count-1 {
 				msg.end_blocknum() - first_blocknum