54Gb of your SSD is not partitioned. You could make a second partition, but honestly, that space should be on your c: drive. SO i recommend that you use partitioning software like this to resize your c: partition to occupy the whole drive: https://www.paragon-software.com/home/pm-express/
Or make a USB drive with this: http://gparted.sourceforge.net/liveusb.php