Final answer:
The phrase 'says it all' implies that the chart presented is self-explanatory and effectively communicates all the necessary information, indicating the presence of strong evidence or statistics.
Step-by-step explanation:
When the speaker refers to the chart by saying it says it all, they suggest that the chart is self-explanatory and comprehensively presents the information or point being discussed. The phrase implies that the chart effectively communicates the message and that nothing more needs to be said to understand the situation or argument being presented. This can indicate the presence of compelling evidence or statistics that fully support the speaker's point without requiring further elaboration.