“Smart” totaling means that duplicate data is counted only once in any subtotal or total. Salesforce uses “smart” totaling when you run reports that include duplicate data in any of the columns chosen for summing or averaging.
For example, suppose an opportunity has two products, and you run the Opportunity Product Report with the total opportunity amount selected as a column to sum by. The amount appears twice in the details of the report, once for each product on the opportunity.
In this case, “smart” totaling correctly calculates any subtotals, grand totals, and averages, adding that opportunity amount only once.
Note:
For dashboard components, “smart” totaling isn’t used. For example, in a dashboard table, the total displayed is simply the sum of the values listed in the table.
If you can’t see the The button to add formulas Add Formula option in the Fields pane of report builder, change your report format to summary, matrix, or joined. Formulas don’t show up for tabular reports.
2. Summary or Matrix Report Grand Total appears with incorrect total – https://help.salesforce.com/articleView?id=000313071&type=1&mode=1
3. Report and List View runtimes vary
Salesforce has a caching system with respect to reports and list views that improves performance on queries that have been run recently. The data from recently run queries is stored in logical memory. The term for this is cached data. When data is cached, queries run quicker because reading from logical memory is faster than reading from a physical hard drive.
Note: The amount of time for which the queries are cached is dependent on a number of variables and may not always be consistent.
If the report is timing out, running it again may reduce the runtime and allow it to complete successfully.
Reasons why a report may run slowly include:
a. It is querying too many objects
b. It is dealing with intricate relationships.
c. It has too many fields.