Hi Qiao,
It is a bit of a mystery to me why the console is not showing the right size. Could you try to install BEAST v2.7.0 and see whether the problem persists? It may be a good alternative if the kind of analysis you want to do only relies on packages that are already migrated to v2.7.0.
An alternative is to use BEAST from the command prompt: in the folder where you have installed BEAST, there is a folder called "bat" that contains "beast.bat". You can run that by opening a command prompt and run
\path\to\BEAST\bat\beast.bat beast.xml
where "\path\to" the path to where BEAST is installed, and "beast.xml" the name of the XML file you want to run.
Regards,
Remco