What to expect day 3?

Millie
Hi all
On our second icsi cycle. First cycle no fertilisation, this cycle we have two fertilised, on day 3 one is 8 cells which they tell me is perfect, the other is 13 cells. The lab didnt sound too concerned but everything I read says 6-10 cells ok. Anyone know anything about why one might be dividing this fast and what the likely outcome might be??? 
Thanks!!