The short answer is that your combining (unsuccessfully) a categorical series (the columns) with interval/ratio series (the line charts). So, Excel doesn't know how to plot your categories (columns) on an interval scale (the current X axis).

To verify this, just add a second horizontal axis and format the `Position Axis`

to `On Tick Marks`

and you'll lose half of your first and last columns (because they're centered on the 0), but your XY series will line up exact center of the columns, like this:

To correct it, the easiest thing to do is create a new chart.

- Create a column chart with your current columnar data.

- Add your first XY data series to the chart-it'll only allow you to add your Y component, because you don't have an XY chart.
- Select your XY data series, right click and change your series chart type to XY.
- Use the select data dialog box to add the correct XY data for that series.
- Configure your secondary axis (horizontal and vertical). Because your using categorical data (categories 1-10, named 8, 40, 72...296) on your primary horizontal axis, you'll have to adjust your secondary horizontal axis to match it. For the data you'll have you'll need a minimum -8 (8-16, or 8- 1/2 of 32) and max 312 (296+16, or 296+ 1/2 of 32). This is what the two axis look like next to each other:

Also, this only works for evenly distributed values, if your values follow different distributions, you'll have to use a different (likely more complex) method.

- Use the select data dialog box to add the other XY data series for the chart.

Good luck

**EDIT: I forgot to mention that mine is Excel 2010, but my experience has been that it should still be ok in 2013, but I haven't tested it.**