Where to place the splitter

Hello all... My CC has fitted a joint about 1 mt in front of my modem which coverts from the black external cable into the white internal cable... Do i fit my splitter at that joint or at the point of entry into the modem? or does it matter ?
Sorry if its a dumb question !

Leave the original connections alone and fit the splitter immediately before the modem/cable box.

Splitter position

Thanks For that .. am still sliding down that learning curve .. back onto the haynes manual tonight.
ta