Mac partitions

Received new 5TB My Book today. Part number WDBBGB0040HBK-NA
Erased to HFS+journaled.
Tried to partition.
It refuses to allow a first partition of 80GB,
Seems that there is 1.1GB of something hidden away on the device.
Has any Mac user successfully partitioned one of these things?
We have several older WD externals happily running with about 15 partitions (different OS versions, etc).

Hi n6ac,

Please refer to the link mentioned below:

Thanks, but that is nothing like what I encounter.
Disk Utility (on Mojave, High Sierra, and Snow Leopard) are unable to make the first partition anything greater than 20GB (it seems to have some hidden files, stuff I do not need or want).
Second and third partitions only set to 40 GB even though I am setting all for 80GB.

… n6ac