The mark that you'll find on the left sidewall of your skis is the recommended mount point, ie -3 cm from the exact center of the ski.
Usually, the best way to determine your mount point is to think about what you're going to use the skis for. If you're planning to do a lot of spinning, jibbing, or park riding, -1 or center might be your gig. If you want them as more of an all mountain ski, then go recommended.
Personally, I use mine as park skis, so I'm at dead center.