fix the sum of header Range

handler.go

@@ -410,9 +410,12 @@ func (cr *Cluster) handleDownloadOSS(rw http.ResponseWriter, req *http.Request,
 			rg := req.Header.Get("Range")
 			rgs, err := gosrc.ParseRange(rg, size)
 			if err == nil && len(rgs) > 0 {
-				size = 0
+				newSize := 0
 				for _, r := range rgs {
-					size += r.Length
+					newSize += r.Length
+				}
+				if newSize < size {
+					size = newSize
 				}
 			}
 		}