With Distinct Ads Feature shopclass theme show unique ads on front page in latest listing section. Because some time your latest page get’s crowded with only one category ads because they are latest. Distinct ads may not necessary show different listings but this feature makes sure that no category will repeat in listings at home page.(Some short of emulating random but better performing function).
To enable it visit: Shopclass Settings=>Theme Settings and check Homepage Settings Section
Check on Enable Distinct Ads and Save Settings.