[This post makes incorrect assertions. Sorry.]

[i]Hello, 2 of the achievements cannot be reached due to wrong description/logic.

One achievement requires 2 mines with 30 miners in each. Maximum number of miners is 15, you cannot put more miners in a mine.
Similarly, an achievement requires 30 stonecutters in a quarry. Once again, this is impossible.

Please fix this.[/i]


Update:
As it turns out, you can actually increase the number of miners and stone cutters using the up arrow next to [X of Y] text after selecting it.

Thanks to TheEddevilish for explaining this.

Actually, the max number is 30 workers. The default number of workers that can be assigned is 15, but you can change this from the menu that appears when you select the mine. The same goes for most other production buildings.