What is the duration for which the instance would be charged if terminated within 30 seconds?

The duration for which the instance would be charged depends on the cloud service provider's billing policy.

For example, with Amazon Web Services (AWS), you are billed for any hour in which a instance is in a "running" state. If you start and stop an instance multiple times within a single hour, you're billed for each of those hours.

So, if you terminate an instance within 30 seconds, you would still be charged for a full hour as AWS charges by the hour, not by the minute or second.

However, this can vary with different providers. Some cloud providers may offer per-minute billing, so it's best to check the specific billing policy of your cloud service provider.