Confused by report - 'made it' to Day 3 or not?

Hi all,

I'm confused by a Day 3 report from my clinic. It says that 6 of my embryos are at the expected stage (at least 6 cells), the other 4 developing more slowly/reduced quality. What does this mean? Does it mean they haven't 'made it' to Day 3 stage and therefore unlikely to blast?

TIA! x