It sounds like the issue you're experiencing is related to the way Excel is interpreting your data. By default, Excel will sort the data in a chart's data table based on the order in which it appears in the source data range. However, if the chart is using a different order for the categories on the X-axis, this can cause the data table to appear in the opposite order.

To fix this issue, you can try the following steps:

1. Select the chart and click on the "Design" tab in the ribbon.
2. Click on the "Select Data" button in the "Data" group.
3. In the "Select Data Source" dialog box, click on the "Switch Row/Column" button.
4. Click "OK" to close the dialog box.

This should switch the order of the data table to match the order of the categories on the X-axis. If this doesn't work, you may need to manually rearrange the data in your source data range to match the desired order of the categories on the X-axis.