Replying to Salomon 2012 mounting help

I have last years 2012 which i took to get mounted yesterday and when i told the guy to mount them dead center he said that they shouldnt be mounted center because they arent symetrical and to mount them at the progressive sstance? Is progressive the center or what im confused? and i have always had my skis mounted center i had ar7s mounted center last year. Should i call back and tell them to mount it dead center or just leave it at progressive?+k for help