I am guessing you have some negative numbers as well as positive numbers in your chart. When you make a chart of that data, the X axis line is going to shoot off from the minimum Y value (at the bottom of the chart), not at Y=0. While you cannot change that behavior, you are able to turn off the X axis line and put a reference line coming off at Y=0. The X axis category labels will still be at the bottom of the chart.
- Select the chart
- In the Axis tab / Value Y, turn on a reference line. Set it to custom at 0.
- Select the reference line and change the weight of it if you think it is too thick
- In the Axis tab / Category X, uncheck the box for Axis line.
- You might want to put a border around the entire in the chart (which I did not do in the screenshot below. There is a checkbox for the border in the Chart tab.