Removed unnecessary (double) casting of interval_to_seconds result to interval_t.

src/main.c

@@ -42,7 +42,7 @@ int parse_arguments(const int argc, const char * const * const argv,
             *wattage = (wattage_t)atof(argv[2]);
             ++pos;
         } else
-            *interval += (interval_t)interval_to_seconds(argv[i]);
+            *interval += interval_to_seconds(argv[i]);
 
     return 0;
 }