LVM does support shrinking a volume. You would use the following option:
However, it is worth pointing out that shrinking a volume is a lot riskier than extending a volume. So much so, that most paid support vendors (Red Hat, Canonical, etc) do not officially support shrinking volumes. Software like GParted make use of various hacks and cludges to make shrinking work. For example, GParted attempts to move all files to the begining of the volume, leaving all of the empty space at the end where it can be trimmed. It will not allow you to shrink the volume by an amount greater than the free space available.
The recommended best practice is that you backup the data, rebuild the volume to the desired size, and then restore the data. This causes downtime, but it is guaranteed to work.