No, the temporary folder is a setting available in the freenas transmission settings menu. If you didn't edit this then ignore me mentioning it.
You downloads should be ending up in //TORRENTS in the jail, which is not on the dataset you mounted into the jail.
- first off, get rid of that double forward slash, it is just going to make things more confusing.
- second, I assume you actually want your downloads to end up in /mnt/TORRENTS, which corresponds to your PRIME/TORRENTS dataset when viewed from the host FreeNAS system.