Answer:
12, but it depends on if the four eggs were eaten by dad and grandmother EACH (4 eggs each) or if the 4 eggs were eaten combined. If it was 4 eggs EACH, the answer would be 8 eggs.
As well as this, the eggs that fell down might probably still be in the fridge, unless they cracked, were rendered useless, and were thrown away. If the 3 that fell are still in the fridge, then the answer is 15, not including my previous statement.
I can tell this is a trick question, but a good one at that.