Meaning that they didn't launch at the right time to arrive at Mars, due to where Mars is in its orbit currently. It'll pass through the imaginary circle around the sun which is Mars' orbit, it's just that Mars will at a different part of the orbit at that time.
But actually, it seems they decided to just empty the tanks and get as much delta-v as possible, and it'll go all the way into the asteroid belt as a result.
Yes, depending on time of year. They could probably have aimed to hit Mars, but stopping in Mars orbit would (probably) require another burn on the Mars end.
Regardless, like other posts have said, they haven't actually left Earth orbit yet. There's one more burn in about 5 hours.
But actually, it seems they decided to just empty the tanks and get as much delta-v as possible, and it'll go all the way into the asteroid belt as a result.