The description meta tag is pulled from the summary. At the time I built this feature I believe the suggested length was longer. I’ll adjust to the newer recommendations. That said, you can use Custom Summaries if you wish. If a blog post has a custom summary it will use that instead.
Something to note though. If your post has a custom summary and you decide at some point you want to turn custom summaries off, don’t forget to delete the custom summary text from the post(s) before turning off the feature in the Editor stack. Any posts that have custom summaries in the Markdown file will continue to use that data.
I believe it is 160 currently. That is what I will aim for when I update things.