the column labels are initially set when using arrayToDataTable to create the data table

so, instead of using addColumn, you just need to change the existing labels

replace…

data.addColumn("number", '" + SelectedLine1 + "');
...

with…

data.setColumnLabel(1, SelectedLine1);
data.setColumnLabel(2, SelectedLine2);
data.setColumnLabel(3, SelectedLine3);