You can easily show the most recent 10 posts:
[mashup query="post_type=any&posts_per_page=10"]
Unfortunately, if you instead want to use a specific time (like past 30 days), WordPress really doesn’t offer a way to do this in a query string – you would need to use a PHP template tag instead. If you want to take that route please see the documentation for some examples and the WordPress Codex for info about the date parameters: