What is the logic of XY (Scatter) charts?

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I understand that XY or scatter charts require data on the X-axis as well as the Y-axis.

What I don't understand is what the Calc 4.2 User Guide says:

"While constructing the chart, if you choose Data Range > Data series in rows, the first row of data represents the X-axis. The rest of the rows of data are then compared against the first of row data. Figure 39 shows a comparison of three currencies with the Japanese Yen. Even though the table presents the monthly series, the chart does not. In fact the Japanese Yen does not appear; it is merely used as the constant series that all the other data series are compared against."

The example in the user guide shows four rows of data. Only three data series are represented in the chart because they are all compared to the first row of data. The user guide says "the first row of data represents the X-axis." What does it mean to say that the data is represented in the X-axis?

By contrast, when I create an XY chart (attached), I have not seen the behavior described. When there are three rows of data, three data series appear in the chart.

The guide says that this works for data in rows. But wouldn't it work the same for data in columns? In the attached file, I created XY charts for data in columns and for data in rows. I saw no difference.

So, I would appreciate some insights about how data is treated in XY charts. Is the description in the user guide correct? If not, what does it say that is incorrect? C:\fakepath\Margarine syrup butter chart 5-14-19.ods