Excel chart looks too small on screen due to chart displayed as graphic.
Cause:
The embedded chart is displayed as a graphic object on the worksheet.
Solution:
Select the chart and drag a chart handle to resize the chart.
1) Select (click once on) the desired chart. (Handles appear around it.)
2) Click on the handle at one corner of the chart.
3) Press and hold down the mouse button.
4) Drag the handle to resize the chart proportionally.
5) Release the mouse button when the size is satisfactory.
