Antonio, like all the bots, is overrated by at least several hundred points. Still, good for you; I'm sure your skills are improving. Your rating is what it is though.
what does it mean if I defeat a 1500 rating bot?

Bots are much more predictable than human players, and their ratings are often somewhat inaccurate. So, beating a 1500 ranked bot doesn't necessarily correlate to beating a 1500 rated human, and even then your rating probably wouldn't be 1500. That is an advanced bot though, so good for you! I've had similar experiences beating advanced bots such as Wendy (rated 1500), but my true rating is probably nowhere near 1500. Keep practicing though, your skills will only improve! I am aware that this was written 4 years ago.
I defeated the Antonio bot whose rating is 1500. So does this mean that my 'rating' is 1500. I doubted myself so I played 3 more times and I won again and again. So does this mean something cause it would be a relief to tell people that my rating is not 890