Hi
Just going by memory of the instruction sheet for these boards ,i deduced(i think thats a word) that a ventilator meant that the fridge was cooled by air fom the freezer as apposed to being a cold wall type. A combi unit just meaning that it is a fridgefreezer as apposed to a fridge or freezer(i think) Top mount unit i dont know. All the boards ive fitted of this type i never had to do anything with the tabs.