The "Threads" parameter specifies the number of buckets that are rendered concurrently.

I have seen a recommendation to set this to twice the number of processor cores on your computer. I'm not sure why.... maybe each core can efficiently handle two rendering threads.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)