Hi
Don't know what it would be at your clinic, but ours will only let them grow to blast if you have 4 or more embryos. If there are less there's not much point leaving them for 5 days, cause they'll already know which ones are the best quality for transfer.
Your clinic will probably have a similar policy.
In my case, we only got 3 eggs fertilised, on day 3 the best one was transferred, & the other 2 were left to grow in the lab. Fortunately they both grew to blast & are now on ice!!!
Lots of luck for your appointment!!!