diff --git a/Aria/src/main/java/com/arialyy/aria/core/download/SingleThreadTask.java b/Aria/src/main/java/com/arialyy/aria/core/download/SingleThreadTask.java
index c4dc1b65..b6233744 100644
--- a/Aria/src/main/java/com/arialyy/aria/core/download/SingleThreadTask.java
+++ b/Aria/src/main/java/com/arialyy/aria/core/download/SingleThreadTask.java
@@ -44,10 +44,6 @@ final class SingleThreadTask implements Runnable {
   private int mBufSize;
   private IDownloadListener mListener;
   private DownloadStateConstance CONSTANCE;
-
-  /**
-   * speed = (bufSize / 1024) * CoresNum / sleepTime; (8192 / 1024) * 4 / 1= 32 kb/s
-   */
   private long mSleepTime = 0;
 
   SingleThreadTask(DownloadStateConstance constance, IDownloadListener listener,
@@ -71,8 +67,7 @@ final class SingleThreadTask implements Runnable {
     } else {
       BigDecimal db = new BigDecimal(
           ((mBufSize / 1024) * (filterVersion() ? 1 : CONSTANCE.THREAD_NUM) / maxSpeed) * 1000);
-      db.setScale(0, BigDecimal.ROUND_HALF_UP);
-      mSleepTime = db.longValue();
+      mSleepTime = db.setScale(0, BigDecimal.ROUND_HALF_UP).longValue();
     }
   }
 
diff --git a/img/11.gif b/img/11.gif
deleted file mode 100644
index ff6359c0..00000000
Binary files a/img/11.gif and /dev/null differ
diff --git a/img/max_speed.gif b/img/max_speed.gif
new file mode 100644
index 00000000..60d08f04
Binary files /dev/null and b/img/max_speed.gif differ
diff --git a/img/popupwindow_use.gif b/img/popupwindow_use.gif
deleted file mode 100644
index af3df1ce..00000000
Binary files a/img/popupwindow_use.gif and /dev/null differ