Less space than expected

[Zord]

I recently found FreeNAS and ZFS, and I think its great, so before making my own build I decided to test if it is within my abilities to configure it right and organize a dataset which will be shared between few windows based systems.
I made installation in VMware Player, and created 5 drives (with allocated real space on my SSD) - 4 of which will be used as storage and one for the operating system. Each of the storage drives has a size of 4 GB (seen as 4,3 GB in FreeNAS user interface). I am using RAIDZ1 configuration and was expecting to see 3x4,3 = 12,9 GB or around 12,01 GiB, instead I get 7,9 GiB for the pool of which I can use 5,6 GiB in the dataset I made.
There are no snapshots, deduplication, encryption or anything, the space is yet unused. I made several tries with different volumes and number of drives, and I always used the wizzard to create them, the results are similar - a lot of space wasted?
Here are few screenshots I made, I hope will help you to see what I do wrong:

Is it possible this problem to be presented because they are not real hardware drives?
I have seen this thread but didn't understand where my problem is.
Any help will be appreciated.

 

[danb35]

When you create a pool, FreeNAS partitions each disk and, by default, creates a 2 GB swap partition. That's where your extra storage is going.

 

[Zord]

Now I understand, it is that bad only because my virtual drives are really small, its not percentage, what I was afraid of.

Thanks!