The issue is that the data in scientific notation, coming from the .txt files is being interpreted by JMP as character data, not numeric. I am not aware of a method to change that during the reading in of the data, however, it is a simple matter to do that after the data are in the data table. The following modification to your code will make the changes:
:Column 1 << Set Name( "Frequency" )<<data type(numeric)<<modeling type(continuous)<<format("Best",15,7);
:Column 2 << Set Name( "S11 Data" )<<data type(numeric)<<modeling type(continuous)<<format("Best",15,7);
:Column 3 << Set Name( "Result1" );
:Column 4 << Set Name( "S21 Data" )<<data type(numeric)<<modeling type(continuous)<<format("Best",15,7);
:Column 5 << Set Name( "Result2" );
:Column 6 << Set Name( "S22 Data" )<<data type(numeric)<<modeling type(continuous)<<format("Best",15,7);
:Column 7 << Set Name( "Result3" );
Please note the format setting. You can change the format to any JMP numeric format, and it will that format the Graph windows will use.
Jim