Keep in mind, statistically, one should expect about 5/6 of the Imperial population to be from Pop A worlds under CT/MT/T4... and 10/11 from pops A&B... But that's 1/36 and 1/18 of the mainworlds... 61,728,271,600 per 36 worlds is the expected population rate, of which 50,000,000,000 are on the 1 pop A
But the 2d6 throw was never intended to be every world, just the most important in the system. (with subordinate worlds being smaller, they seldom factor in.)
And Mongoose, by adjusting Pop by physicals, makes pop 12 possible. In a subsector, if present, a pop 11 or 12 is going to like be 90% of the pop of the subsector all by themselves...
and to dominate trade for 2-3 jumps around.