A transient is a way for storing cached data temporarily in your database by giving it a name and a timeframe after which it will expire and be deleted.
To clean this dashboard transient feeds, you can either use our plugin Advanced Database Cleaner or execute the following SQL code (which is used by the plugin) directly via your phpMyAdmin:
DELETE FROM options WHERE option_name LIKE '_site_transient_browser_%' OR option_name LIKE '_site_transient_timeout_browser_%' OR option_name LIKE '_transient_feed_%' OR option_name LIKE '_transient_timeout_feed_%'
