It's your responsibility to be able to put it in gear without rolling back a significant distance.
That said, six inches is closer than you should be in any situation.
You actually shouldn't even do any rolling while putting it in gear, since you can keep your foot on the break. It's when you move your foot from the break to the gas, give it a little gas, and ease off the clutch that you need to be quick about, which can be tough before you've had a lot of practice with that particular car.
Engage the parking break and put it in gear, then take your foot off the break and put it on the gas. Give it some gas and ease off the parking break as you ease off the clutch and you should be golden
Just relax and feel the car and you won't have any problems... It took me about two days to learn and now it's basically as if I'm driving an automatic
That said, six inches is closer than you should be in any situation.
Yeah, sorry, it's been a while, I meant the entire process of engaging the engine to the wheels.