Usually, the x-axis is defined by the range of data. It automatically sizes to fit the biggest data point you have in your chart. You can change the limits by double-clicking the axis and setting the "Minimum" and "Maximum" values, but this will just adjust the range and not the points on the axis shown.
On the other hand, you can display the actual points of data on the line chart by selecting the Layout tab under Chart Tools, and clicking "Data Labels". This will show the values next to the points on the line.