Thanks!
No, I have different figures. I'm a bit puzzled by the Arretium population, it should be much higher. Did you build troops there?
And for Segesta I got more or less the same (517 to your 520), but I played on medium unit size, perhaps that's the difference. I'll check.
In any case, 520 is too little for the 2.5% growth it should get, but equals almost exact the 2% growth it has without the 0.5% slaves.
It appears you don't get the slave bonus either.
edit: running on HUGE, gives me 518 in Segesta, I guess there is some rounding issue somewhere. In any case, if you didn't build any units in Segesta, then you surely did not profit from the 0.5% slave bonus.