Ahh… I see what you mean.
It may have to do with the first row having been a Header row. When you changed it, the change may have also affected Numbers recognition of A1 as still a member of a Header column. Note that all labels are shifted one data point to the left, and there is no label for the last point.
Here's what it should look like:
![User uploaded file](https://discussions.apple.com/content/attachment/813527040)
To create this chart, enter the data as shown. Select cells B2-C12, then choose the Line Chart from the Charts button menu. (Note that the category labels for the x axis are in a Header column.)
I changes the Stroke of the last connecting line from solid to dashed, and the colour for that line and it's data point symbols from the default green to the same blue as the first series.
To label all of the data points, I then chose the box containing the category axis labels, then changes the label orientation from Horizontal to Vertical Left, using the pop-up menu in the Inspector. Here's the result:
![User uploaded file](https://discussions.apple.com/content/attachment/813553040)
Regards,
Barry