fix: exact staleness timebound (#2143)

fixes: #2129

Author: alkatrivedi

samples/crud.js

@@ -309,8 +309,8 @@ async function readStaleData(instanceId, databaseId, projectId) {
   };
 
   const options = {
-    // Guarantees that all writes committed more than 15 seconds ago are visible
-    exactStaleness: 15,
+    // Guarantees that all writes committed more than 15000 milliseconds ago are visible
+    exactStaleness: 15000,
   };
 
   try {