Normal
It will likely be sufficient in that I wouldn't expect recruiters to mark you down for writing a standard-sized answer. However, I think you should not focus too much on a particular 'target' wordcount. Instead, I would take the opportunity to simply concentrate on writing the best possible answer, even if this ends up with a slightly higher word count than normal. If you observe the usual norms of conciseness and your write in a very structured and to the point manner, I would not expect recruiters to have an issue even with 500-600 word answers.