the simple answer is that if you want to keep your current programme, you cannot. A summary bar is just that;a summary. It starts on the first day under it and finishes on the last one. Any gaps or non working time dont matter.

If you are happy to change the layout, you can make another summary task at the same level as the 168004 one and give it a new name. this would then separate out the 2 projects as separate. as far as I know, thats pretty much te only options.