Remove µs string before multiply, fix return type (#227)

Co-authored-by: Andrej Mihaliak <[email protected]>

Author: mihaliak

src/Commands/StartRoadRunnerCommand.php

@@ -196,7 +196,7 @@ protected function writeServerOutput($server)
      * Calculate the elapsed time for a request.
      *
      * @param  string  $elapsed
-     * @return int
+     * @return float
      */
     protected function calculateElapsedTime(string $elapsed): float
     {
@@ -205,10 +205,10 @@ protected function calculateElapsedTime(string $elapsed): float
         }
 
         if (Str::endsWith($elapsed, 'µs')) {
-            return $elapsed * 0.001;
+            return mb_substr($elapsed, 0, -2) * 0.001;
         }
 
-        return $elapsed * 1000;
+        return (float)$elapsed * 1000;
     }
 
     /**