I think bitexploder is referring to the "Dunbar's number" which is 150.

https://en.wikipedia.org/wiki/Dunbar%27s_number

From the wiki: Dunbar's number is a suggested cognitive limit to the number of people with whom one can maintain stable social relationships. By using the average human brain size and extrapolating from the results of primates, he proposed that humans can comfortably maintain only 150 stable relationships.