Translation:They are making a graph for that report.
Meaning: They are making a plot for that report.
"graph" or "chart" instead of "plot" should be accepted as well.
Indeed, "plot" is sometimes used as a verb in American English (e.g. to plot a course for somewhere), but it is obsolete for referring to a graph, chart, or table. The noun "plot" is now limited to a scheme or plan, probably for something nefarious (e.g. the FBI intercepted a terrorist plot).