if your value is "30" it means 30 Seconds. 1800 would be 30 minutes.
I didn't mod livonia yet, isn't there a zombie_territories.xml? There you could look for the coordinates of your base (iZurvive DayZ & ARMA Map: Chernarus+ Terrain) and delete the line. So I got rid of the zombies lurking in my base in vybor.