Adding Columns

I am trying to make a design table and I want to add somecolumns for equation purposes. When I do that I get an error about"Column heading "No. of Full Louvers" contains an invalid featurename "No. of Full Louvers".

Exiting design table without completing model update.

No. of Full Louvers is in my equations, but when I make the DT itdoesn't get there.
RobSolidworksConfigurations design Tables