When you are presented with graphic material in a reading passage, pay particular attention to the title of the graph. Often, a statement is included that gives you the source of the information. Read that statement. The labels on a graph are vital to understanding the information, particularly the units that numbers are presented in.
For example:
Are the numbers in dollars, thousands of dollars, millions of dollars? Are you looking at percentages?
Very often, this information is in small print; do not overlook it. Finally, you must consider the relationship of the graph to the written material.