The numbers that make it to blast are fairly low, it seems.

In the two cycles we've been able to grow to blast, we've got 4 from 18 and 7 from 20. However, of those 11 blastocysts, only 4 thawed to be usable embryos, but we had a few other issues with fragmentation, PCOS and bad OHSS on those cycles. Mostly related to getting such ridiculously high egg numbers to start with.

My clinic would not grow to blastocyst unless there were more than three embryos to work with, which should help give you some idea of what sort of numbers the clinic would expect.

I hope your super-blast is growing like mad and you do manage to avoid the need to do another stim cycle. Although, subsequent cycles are never as bad as the first as the clinic has more of an idea about how you respond.

BW