my drive just arrived....

running the test to make sure it is brand new, also no errors
hdds usually like if says 1tb, you don't actually get 1tb usable space. probably slightly less.

for example my seagate 1tb is actually only 931gb usable space.
also 512 vs 4k sector drives, the later has more usable space on a 2tb+ hdd, because it's more efficient as it uses less space for stuff like error correction etc. so for 2tb+ hdds always get the 4k native models. you only use 512 when using an older OS, which i don't recommend doing
total read 770gb seems a bit low.... can u check whether part of your HDD is unallocated ? i suspect that is the problem for your particular case. to check, either use something like AOMEI's partition assistant app, or, go to computer management in windows and check if the drive in question has any partitions unallocated 
PS: i checked the same properties windows as you, and mine correctly states total capacity is 931gb. so yours is definitely weird 

can you try download aomei partition assistant and check if there is any partitions ?

also try use hd tunes and run a block scan, then view the smart info 

i'm an ameteur as well, but if i had to guess, either it's an unallocated partition, or .... it's bad blocks that have been reallocated which would make the usable space much smaller. The last is just my guess, cause i don't know if it would actually do that 

but what else could it be ?