Ring Intercom & BTICINO 344252 - cable instructions unclear, support not helping

hey all!just wanted to set up my ring intercom with a bticino 344252 - ring tells me it's compatible, tells me to use the B cables, but then is not providing *clear* instructions. it says"insert wire B-2 into port BUS""insert wire B-1 into port BUS"however BUS consists of four ports and four cables in there already, how am I supposed to approach this? does B-1 equal to the first cable and B-2 to the second cable or is there another information that I'm supposed to know?I tried calling ring support but they say to go to an electrician and they don't provide more information. this is ridiculous, i literally opened up everything and am capable of adding the cables, i just need to know out of the 4 ports, which cable should be added where?can anyone provide some more guidance?thank you!