Hi Sheldon,
Welcome to the Box Community, I'm happy to help!
The Sync/Unsync feature that you see in Box.com is a function for Box Sync app and does not have any effect on the Box Drive app. Box Drive doesn't have the function to selectivity choose folders they wish to sync, the app automatically download your folders/ files in a form of cache data into your machine.
Box Drive's cache size limit is set to 50% of your available local disk space with a maximum limit of 25GB and a minimum of 1GB. I recommend checking out the following article if you wish to learn more about Box Drive cache and should you need to adjust this maximum cache limit for Box Drive:
Let us know if you have questions, and we'd be more than happy to help!
Regards,
Okay, thanks for clarifying. I'll take a look at the article.