it is generally not good practice for the admin landing page of a large forum to (for example) constantly count over 100,000 files and byte sizes on disk and sum 100,000 lines of text in the database each time the forum admin hits that page, unless they are debugging something related.
as gizmo mentioned, there is a note detailing this within the /admin/dashboard.php file. there is another one mentioned on the control panel's debug setting toggle.
from Control Panel > Primary Settings
FORUM: Page generation times, number of queries, memory stats, compression, forum server time, and forum software build information is displayed on the page footer. HTML Page minification is also disabled while debugging is enabled.
CONTROL PANEL: File Attachments stats are generated on the dashboard. Sites with a large number of file attachments may experience a delay in producing the page.
Warning: With this option is enabled, any time there its a database connection error, database connection information is displayed to everyone visiting your forums. This includes your database name, database user name, and the table name that failed connecting to. Passwords are not displayed. Debugging is safe to enable, but for security and overall forum performance, it should remain off.