Since Tig's uses git-show(1) to display diffs you can use the --stat
diff option. For example:
$ tig --stat=200,180
Unfortunately, there is no option to scale it by a percentage, so you have to do that manually.
Here's the documentation for the option:
--stat[=<width>[,<name-width>[,<count>]]]
Generate a diffstat. By default, as much space as necessary will be used for the
filename part, and the rest for the graph part. Maximum width defaults to terminal
width, or 80 columns if not connected to a terminal, and can be overridden by
<width>. The width of the filename part can be limited by giving another width
<name-width> after a comma. The width of the graph part can be limited by using
--stat-graph-width=<width> (affects all commands generating a stat graph) or by
setting diff.statGraphWidth=<width> (does not affect git format-patch). By giving a
third parameter <count>, you can limit the output to the first <count> lines,
followed by ... if there are more.
These parameters can also be set individually with --stat-width=<width>,
--stat-name-width=<name-width> and --stat-count=<count>.