POS of Compounds

[EDUCATIA SUPERLATIV]

Hi,

I tested using compounds.

I create a compound from various objects.

I obtain an initial COMPOUND.pos.

After I rotate the compound by 180 degrees by axis = Xdir, with the center of rotation = compound.pos I obtain a mirror model,  but

If I rotate again under the same conditions

the POS of compound change his location, is different from the initial !!!?

I understand is something related to the local/global coordinate system, but

If I rotate around COMPOUND.pos should I obtain the same results?

Or not?

Best regards,

Ciprian

PS: some short examples or specific links to existing examples please