Description of problem:
I tried to change the capacity of new volume from 160 GB to 140. I did it in manual partitioning.

Version-Release number of selected component:
anaconda-18.16

Additional info:
libreport version: 2.0.14
cmdline:        /usr/bin/python  /sbin/anaconda
kernel:         3.6.1-1.fc18.x86_64

description:
:The following was filed automatically by anaconda:
:anaconda 18.16 exception report
:Traceback (most recent call first):
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/size.py", line 79, in _parseSpec
:    raise ValueError("invalid size specification", spec)
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/size.py", line 137, in __new__
:    self = Decimal.__new__(cls, value=_parseSpec(spec))
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/gui/spokes/custom.py", line 1081, in _save_right_side
:    % str(Size(spec="%f MB" % device.size)).upper())
:  File "/usr/lib64/python2.7/site-packages/pyanaconda/ui/gui/spokes/custom.py", line 1948, in on_apply_clicked
:    self._save_right_side(self._current_selector)
:ValueError: ('invalid size specification', '-1.000000 MB')