Also wanted to add that with both of my transfers I had quite a bit of fragmentation. The first time I had a 7 an and 8 cell both grade 4 (Scale of 1-5 with 1 the best) in terms of fragmentation. Had a CP that cycle (think it was due to progesterone, not the embies). The second time I had an 8 and a 10 cell, again grade 4. One stuck, and I'm 9 weeks today. So try not to worry too much about fragmentation. My RE said the number of cells is the better indicator of whether they will continue to grow and divide... so right around 8 is your target- but many women have 4,5,6,7 cell embies go on to make beautiful babies.
Ultimately, they don't really have a great way to tell at this point which embies will stick around for the long haul. What they do inside you is so different from what they do in the lab. Good luck!