A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
It would be nice to see the data, and to know what type of chart you are making.
I you have 2 columns of numbers, and both have a header (i.e. some text above the top numbers), then should you make a Line chart, Excel will treat the first column as a data series. The x-values will be 1, 2, 3....
It sound like you really need an XY chart if you with to plot y against x.
BTW: if you must make a Line chart just take the text heading off the first column; it can be restored after making the chart.
best wishes