Most telephone lines only need 2 wires to make the connection to work with the landline telephone and DSL line.
On my landline telephone there are only 2 wires connecting the telephone line from the outside telephone box to the inside telephone box.
Those wires are green and red and those are the only two wires that my telephone needs and the extra wires in the telephone wire are to carry more than one telephone line so if you have one wire with 4 strands of wire for the telephone then that would mean that you could install two telephone jacks in the same location without running extra wires.
But if you only need to run one telephone line then you only need the 2 wires for the telephone line to operate and you can disregard those extra telephone wires.