Explanation:
Box 1: Dual
Customer should use the dual storage mode.
Dual: Tables with this setting can act as either cached or not cached, depending on the context of the query that's submitted to the Power BI dataset. In some cases, you fulfill queries from cached data. In other cases, you fulfill queries by executing an on-demand query to the data source.
Note: You set the Storage mode property to one of these three values: Import, DirectQuery, and Dual.
Box 2: Dual
You can set the dimension tables (Customer, Geography, and Date) to Dual to reduce the number of limited relationships in the dataset, and improve performance.
Box 3: DirectQuery
Sales should use the DirectQuery storage mode.
DirectQuery: Tables with this setting aren't cached. Queries that you submit to the Power BI datasetג€"for example, DAX queriesג €"and that return data from DirectQuery tables can be fulfilled only by executing on-demand queries to the data source.
Queries that you submit to the data source use the query language for that data source, for example, SQL.
Box 4: Import
Import: Imported tables with this setting are cached. Queries submitted to the Power BI dataset that return data from Import tables can be fulfilled only from cached data.
Reference:
https://docs.microsoft.com/en-us/power-bi/transform-model/desktop-storage-mode