The thetao datasets are quite big 8.3Gb, add size to md

Author: sverhoeven

setup.md

@@ -253,7 +253,7 @@ local machine and go [here](#gitHub-account-(advanced)).
 If you are planning on running ESMValTool on your own machine, please make sure
 that you are able to download CMIP data and that you have several GB of space
 available to install conda & ESMValTool, but also enough to make a copy of some
-data.
+data (12Gb).
 
 For this tutorial you can download the required data files by