Allocated Memory around a 5th

I using the below card and notice around a 5th of the cards memory is allocated.

Why would this be?


Windows 10 x64



Device #1: GeForce GTX 1080 Ti, 2816/11264 MB allocatable, 28MCU


Command used - 
hashcat64.exe -a 0 -m 500 -w 3 --status --status-timer=8 -p : -w 3 -O --gpu-temp-abort=85 "C:\hashes\root.txt" "C:\wordlists\sorted-wordlist"

Also when the cache is built for a word list,  where is this stored?
Word-list is 65GB

Thanks.