Specific knowledge means that these are things that you can learn with some effort and study. They should not be broad categories like “security”, “design”, or “server-side development”. They should be things you know or know how to do, not things you “have experience with”. And they should be specific enough that somebody can feel comfortable saying they understand the topic or don’t. Most of the things I list below are topics, but I try to lay out a specific set of things that you would need to know to understand it.