diff --git a/src/tampermonkey/common.js b/src/tampermonkey/common.js
index 4bb0e0e7ac29cdc1abd99679ccfe570ce2542b0b..cd59185820611704ae85dedf8e3a19030404762f 100644
--- a/src/tampermonkey/common.js
+++ b/src/tampermonkey/common.js
@@ -6,6 +6,6 @@ config.duration = (config.interval || 0.1) * 60000;
 Object.defineProperty(global.config, 'duration', {
     get: function () {
         let interval = (config.interval || 0.1) * 60000;
-        return common.randNumber(interval - interval / 2, interval + interval * 2);
+        return common.randNumber(interval - interval / 2, interval + interval / 2);
     }
 });
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