Final answer:
The dashboard component that shows a grand total across data is a Metric, which succinctly displays key summary values.
Step-by-step explanation:
The dashboard component that displays a grand total across a set of data is a Metric. A metric component in a dashboard is specifically designed to present a single key value; it is particularly useful for displaying a summary or a grand total, such as total sales, total customers, or other aggregated totals that give a quick snapshot of performance. While other components like pivot tables, charts, and gauges can show data in different formats, metrics are the simplest way to represent a grand total. For example, in a sales dashboard, a metric could be used to show the total revenue for the quarter.