chore: Clarify code comment to differentiate theoretical max and expected max

Author: lqiu96

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/DatastoreOptions.java

@@ -55,8 +55,9 @@ public class DatastoreOptions extends ServiceOptions<Datastore, DatastoreOptions
   public static final String LOCAL_HOST_ENV_VAR = "DATASTORE_EMULATOR_HOST";
 
   // Default to a slightly larger channel count to handle a larger initial QPS. The initial
-  // configuration should be able to handle a max of ~500 QPS as each gRPC channel can handle
-  // 100 max streams (limited by Google Middleware). This default relies on the ChannelPool
+  // configuration should be able to handle a max of ~500 concurrent streams as each gRPC
+  // channel can handle a max of 100 streams (limited by Google Middleware). The initial
+  // configuration aims to have a max of ~250 concurrent streams and will rely on the ChannelPool
   // to resize according to the client's average load.
   public static final int INIT_CHANNEL_COUNT = 5;
   // Default to be larger than Gax's default (2) to better scale with spikes in requests