Disk Details info is incorrect

Hello,
I installed CWP on my new vps - KVM Virtualization Type, SSD 40GB
everything running fine, but I noticed that there was something strange in Disk Details info.

CWP says:

Filesystem      Size  Used Avail Use% Mounted on
/dev/vda1       8.4G  3.2G  4.8G  40% /
tmpfs           939M     0  939M   0% /dev/shm

Why 8.4 GB?
I have 40GB space...

I have other vps, also KVM with 30GB SSD and CWP says:

Filesystem      Size  Used Avail Use% Mounted on
/dev/vda1        30G  7.6G   21G  27% /
tmpfs           947M     0  947M   0% /dev/shm

Here everything is correct in the 2nd vps
but why on my 1st vps CWP says 8.4 GB space instead of the real 40GB ?

=============
EDIT:

Disk Details page says:

Fdisk info:

Disk /dev/vda: 42.9 GB, 42949672960 bytes
255 heads, 63 sectors/track, 5221 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00065368

   Device     Boot      Start         End       Blocks      Id   System
/dev/vda1   *           1             1110      8910656   83   Linux
/dev/vda2                1110        1175      524288     82   Linux swap / Solaris
/dev/vda3                1175        5222      32507040  83   Linux

Software RAID:

Personalities :
unused devices:

Partition info:

Filesystem      Size   Used  Avail   Use% Mounted on
/dev/vda1       8.4G  3.3G  4.7G    42%  /
tmpfs             939M     0   939M   0%   /dev/shm

What should I do to get 40GB space?
It does this mean that I have 8.4GB available?
The rest 32GB on /dev/vda3 are available or not?
What to do in this case, can I fix it or my hosting provider should make changes to disk?

It says on the page: "If you are running CWP on VPS than you do not have disk details as disk is virtual!"
So that's the problem

you should contact your hosting provide regarding disk space issue.