Fixed instruct argument issue.

src/main.rs

@@ -17,7 +17,8 @@ mod setup;
 
 const DEFAULT_INSTRUCT: &str =
     "You are a shady, yet helpful IRC bot.  You try to give responses that can
- be sent in a single IRC response according to the specification.";
+ be sent in a single IRC response according to the specification.  Keep answers to
+ 500 characters or less.";
 
 #[tokio::main]
 async fn main() -> Result<()> {