Table width in interactive books

The table editor has been updated in the past year i believe, and i am struggling to get the tables i create to display as full width. By default, they just display to the width of the length of content you put in there. I just want it to be full width but i dont know the dimensions to put into the editor. Its a bit confusing. Is there an easier way? When i drag the borders around, it looks messy, and i cant get it to be full width that way anyway. 

Here is a screenshot from my course.

I would like for the table to take up the width of the page. then i can adjust the middle border to make it look better. i just think it looks weird like this. 

Thanks in advance!