Can I make a row with more than 6 columns?

I want to put a row under my featured image that has 8 or 10 columns. In each column, I want to put a logo of a company we have done business with – meaning a horizontal string of 8-10 logos horizontally under my featured image. (here’s an example: http://www.jillkonrath.com)

The problem is that it doesn’t seem like I can make a row with more than 6 columns.

I add a row with the Virtual Composer. Then I click on the custom number of columns icon. It appears that I should be able to enter the following:
1/8 + 1/8 + 1/8 + 1/8 + 1/8 + 1/8 + 1/8 + 1/8
However, it doesn’t work. I get an error as if this is the wrong format to define the columns I want.

How can I get 8 or 10 columns in one row?

Thanks,

Kevin