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!