wd,
If your series is B5:B10, and "you specified the data series in columns."
You have one column of information to plot "B5 down to B10".

"wd" wrote:

I am new to excel and trying to understand legend factor in a chart.
If I selected cells B5:B10 as the data series for a chart, & specified the
data series in columns. What is my legend?
B5:F5, C6:F10, B5:B10, impossible to determine from info given above.