Why is delay a set?

objectifier-module.nix

@@ -41,13 +41,13 @@ in {
         type = int;
         description =
           "Maximum age of a file (in seconds), after which it will be removed.";
-        default = 60 * 60 * 8; # 8 hours
+        default = (60 * 60 * 8); # 8 hours
       };
 
       delay = {
         type = int;
         description = "Time between cleanup sweeps.";
-        default = 60 * 10; # 10 minutes
+        default = (60 * 10); # 10 minutes
       };
     };
   };