Is the age gap too big?

This guy comes to my job a lot and he’s been trying to date me for a while now. He looks extremely young so I thought he was in his early twenties but he’s 28. Im only 19 so I’m wondering if that’s too much of an age gap. He seems really genuine. He doesn’t know how old I am yet so he’s not trying to take advantage of me for being young or anything like that. Is it too much in your opinion?