The math is more complex. You have to use a binomial distribution to calculate your chances. But the general numbers are somewhere in that area. I calculated 2300 matings for a tribe of 6 to have 98% chance.
That also assumes you are online 24/7 for the entire period to get all the boxes before they despawn. I had one despawn while I was trying to get through my dodo army to get to it. Most people need to sleep,eat, have jobs or school and can't be online for 192 hours straight.