Thing is... you might think of this like population growth, like rabbits: if you have more rabbits they give birth to more rabbits.
But a colony has only one queen. All of the ants have the same mother. The constraint factor on growth is having enough nurse ants and foragers to feed and care for the next generation. Somehow the queen senses the need to lay more eggs and boy can she go! Up to 100 eggs a day in the high summer for some species.