The hatcheries use whatever they have extras of as the 'packing peanuts'. Usually this is a mix of breeds, mostly sexed cockerels. Maybe some random extras. They need to ship out the day's hatch that day, as they can't survive the shipping after they are more than a few days old and are no longer relying on the remnant yolk. So whatever they have- straight run, cockerels, or other extras would go in those boxes.
They also say there is about a 10% chance of error in sexing. So about 1 in 10 of sexed pullets may accidentally be a cockerel. The opposite is probably also true. So in a box with 20 packing peanut cockerels- there may be 2 hens (more or less). I also would bet that if the chick 'sexer' has an ambiguous chick- meaning they are not sure which it is- they would likely err on putting it in the cockerel or peanut bin. So I would also say, as you have them and have the set up to care for them- wait it out. See what you have for sure before deciding what to do with them long term. What do they look like right now? Are they all the same or do you have a mixed bunch of colors and combs?