The rice congee is overcooked.
这粥煮过火了。

讲解：
Overcook就是煮的时间过长了。Undercooked就是火候不够。

Overcooked means it's been cooking too long, and maybe now tastes rubbery – or if its meat, it's all dried out. If it's black, then we say it's burnt, but that's really bad. If something hasn't been cooked long enough, then we can say it's undercooked.