I think this particular rock is about 800m in diameter. That would probably not kill us completely, just be the most catastrophic natural disaster in the history of humanity.

But jokes aside, I think the probability of altering the orbit to hit the earth practically non-existent, especially if you hit it when it is relatively close. You would want to hit it when it is the furthest away from earth to maximize your impact, so something > than 2AU or > than 300,000,000km.

Or maybe a metric/imperial mixup

The physics of irony :)