Alien bursts, matures, morphs its former host into an egg. All in the space 4 or 5 hours. Multiply depending on number of available hosts, with gestation times of around 16 hours, give or take.
Queens, on the other hand, take about 3 days to gestate and another 3 days before they start laying.
Once they do, of course, you have lots and lots more eggs.
But given a large number of available hosts, you could have a bunch of Aliens already setting up a hive in those 6 days.