After reviewing the video more carefully and listening to the hostile exchange, you are right that he was already standing too close. Then black man pushed him, and white man dared black man to put hands on him again, and said that black man had already put hands on him twice (the first time not on camera), and said he would press charges. From what little I gather re context, black man was defending one of the two fellows behind him, and told white man that he was always harassing people. Black man speaks with Caribbean lilt. White man seems to be habitually contentious fellow.
Good observation. I missed the part where the white guy says, “That’s twice.” Maybe the first time was off-camera, but then, maybe the white guy pulled the same stunt the first time - stepping up real close to the guy.
Note: In another article, the black man is quoted as saying he’s from Cameroon in Africa.