Unallocated space is not a separate partition, it's simply dead space until it's allocated for use and formatted.
Your full Drive capacities will always be shown, partitioned/formatted or not; that's how you can tell how much physical space you have on the Drive, regardless how the Drive itself is set up.
As Jay said, you always see your entire drive even if it's not all allocated. If you want to use the full drive space, you'll need to extend the partition you have on the drive already so that it fills the entire drive.
The second screenshot was referencing the active partition on Disk 1. I think he was showing the options were available for that, but not the unallocated space.
Why do you want to delete the partition when you can use it. Windows has a 2TB drive limit. To get around that you need to convert the drive to GPT. To do this right-click on Disk 1 on the left and select Convert to GPT Disk. You can then either create one 2.7TB partition or divide it up into smaller ones. See the reference below for more information. Of course this will destroy anything already on the drive so you need to do this before you start using it.