NGUI comes with a component called UITextList that does this for you. It doesn't use a table, but it does use one label that's scrollable and supports many paragraphs in the "latest on the bottom" style. As a bonus it's way faster than using a table.
Off the top of my head, the UITable should be on a child game object of your widget, not on the widget itself. You also have the table's direction set to be "down", when I'm guessing you will want it to be "up" instead.