I have a 2013 Mac Pro with 32 RAM, a 1 TB SSD drive, 3.5 GHz 6 core Intel Xeon E5, AMD FirePro D500 3 GB Graphics card, running OS 10.13.3. I have four external drives hooked up to it: 2 via a Lacie Thunderbolt 2big enclosure (in a JBOD Raid), and 2 spinning drives hooked up via USB 3.0. I'm running out of hard drive space and a checkin About this Mac shows that my System is using 513 GB of memory (see attached screen shot). This seems like a lot. Is this a typical amount, or is something else going on? Thanks!