configuring X offset for dual hotend

I have installed dual V6 on my delta effector, the nozzles are 30mm apart so i set:

extruder.hotend2.x_offset 30 # x offset from origin in mm

I would like to have the print still in the center, but in this way is offset.
so I changed the x values to:

extruder.hotend.x_offset 15 # x offset from origin in mm
extruder.hotend2.x_offset -15 # x offset from origin in mm

now it prints with a distance of 60 mm between hotend 1 and hotend 2, why ??
I can't figure this out
what values should I put to print in the center ?
thx!

is this forum dead ?