When Kitty and Robert are talking about their embryos, Kitty says they 4 double As and 2 ABs. When talking about embryos, there should also be a number from 1-6 in front of the letters. The numbers indicate how large the embryos got, with 6 being the best. The combination of 2 letters A-C indicate how good the size and shape of the cells look (uniformity in size/shape of the cells, fragmentation, etc.) and the number of cells in each embryo.