Main Page - Opens with Category

Hi I have just installed Ver 1.3.5 and would like to achieve the following.

I currently have two main categories each with apx 10 / 15 sub categories.

Upon going to the site I would like for the main two categories to be expaned, I can acieve this with a single categories by adding the Cat ID in the following field "Main Page - Opens with Category" but would like to know If I can add a second ID aswell.

I have tried using "1, 2" etc, but nothing.

I have also just noticed that for the above to work I have to enable "Always Show Categories on Main Page" which shown the relevant categories at the botton of the page, which I could do without.

Your advice and guidance will be greatly appreciated.

Thanks

Sab