How does SubjectDeleteMarkerTTL work?

[nhphu]

I want to use KV to store user sessions; they will expire after 24 hours

await session.put(key, value, {ttl: "24h"});

In the description of the ttl property, it says, 'Note that for this option to work, the KvBucket must have the markerTTL option.' But I can't understand how it works or what value I should set, even after reading all the related pull requests