Translation:This restaurant's chicken isn't good.
The real answer should literally be: "This restaurant's chicken meat is not good". That is what it says.
I have no idea why they can't simplify answers to what is really written in Chinese. The problem where we all seem to get caught is that sometimes they want a very literal and exact meaning word for word with the Chinese script, and other times they just make stuff up even replacing some of the Chinese words with English interpretations that are way off. Basically that leaves you in a situation of just guessing.
Wouldn't it be better to have written "这家饭馆的鸡肉不好"? Given a choice between the catchall "个" and more appropriate specific measure words, DuoLingo should always opt for the latter. Better to get in the habit of using them early on than having to force ourselves to unlearn it later, even if it might confuse someone here and there. That's what these discussions are for, anyway.
Ji Fan Dian. Here's the sign outside Loy Kee https://www.quandoo.sg/place/loy-kee-best-chicken-rice-balestier-35200