Why is there not much space for my Ubuntu?

Question

I have a dual system: Windows 7 + Ubuntu. The Windows came with my laptop and I installed Ubuntu without Wubi...

My total filesystem capacity: 303.2 GB, I just do not understand why there is not much space for Ubuntu. Here is a screenshot of Disk Usage Analyzer, where The 新家卷 under media is a disk mounted:

Here are the screenshots of Disk Utility, I even do not know which disk is for Ubuntu

I can delete many films to save space under Windows, but it seems that there is nothing to do with Ubuntu... Could anyone help? Thank you very much

Edit1: As requested, here is the result of df -h:

...@ubuntu$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/loop0             17G   13G  2.8G  83% /
none                  2.0G  716K  2.0G   1% /dev
none                  2.0G  4.3M  2.0G   1% /dev/shm
none                  2.0G  112K  2.0G   1% /var/run
none                  2.0G     0  2.0G   0% /var/lock
/dev/sda3             188G  176G   12G  94% /host
/dev/sda5             100G   99G  1.9G  99% /media/新加卷

Answer 1

I am pretty sure your Ubuntu is installed using Wubi - there are no Linux partitions on the drive. And there is a strange root-level folder /host, which is absent when Ubuntu is installed on a separate partition.

All your Linux files take about 11Gb and they all live in some file on your Windows partition (I see root.disk in the left pane - is that it?)

My understanding is that Wubi disk/file does not grow dynamically. See this for some advice on how to migrate your /home directory to a separate "disk" (or into a separate file) to get some additional space.