ZeXtras Trial Import: 30 Days of email or 30 day old backup?

Just trying to figure out the limitation of the zextras trial and want to clarify something.

When they say we can import a backup thats 30 days old, do they mean that if I create a zXbackup 1 year ago, that the import wouldn't work? Or do they mean that the import will only restore emails dated back to 30 days ago? (i.e will our inboxes only have 30 days worth of email?)

I hope it's not the 2nd.