Foxoq

I think you're referring to the number that tells you your current population and how long before it maxes out.

For example, mine says (958:7D). Thus I have a current population of 958 and seven days before my town fills up. However, I'm not sure if this script calculates it correctly, as the happiness score of your town lowers as the population rises, thus the growth rate lowers as well, complicating things a bit.
Although,

I've had success with it so perhaps they've included the changing rates. Lastly, if you mouse over it, it will tell you when to start expanding in order for your town hall to be fully operational in time for the new population growth.

All this is part of the Kronos script I believe.