I measured mine out.. and recommended is actually more like 5 cm back from true center. However, I am quite positive that the -2.5 cm that line states is back from core center. I mounted mine at recommended and was skeptical at first, but they ride amazing.
So another vote for recommended. Maybe +1.. but thats it.
I don't work @ jibij, but you should go there!!
'Heh Heh ... All Right.' ~Quagmire