A feature of Latte is that it can show a number of e.g. unread notifications directly on the application icon. This also works on my setup, if I add the KDE default panel and change the taskbar in there to Latte via alternatives. However, if I add a normal Latte, e.g. a widget or start it with krunner, Latte doesn't show this unread badge.
I am not sure, if this was clear enough, but using Latte in the default KDE taskbar is pretty shitty and using a normal Latte dock doesn't show the notification count on the icon.
I am sry, after a reboot this was solved. My bad, I think it was because I installed libunity and didn't restart that specific Latte dock after that.