The resistor doesn't help work anything out. Depending on the number of connections between the two sections, it could be used for measuring current. It could even be a
cheap fuse (there are resistors with a specified action energy, so it is possible.) One thing such a resistor does not do is distribute the current evenly in all 9 strings. And so they must be depending on the fact that by the time 25 LEDs are added to a string that the probabilities argue that the distribution of currents will be sufficiently even, whatever that means. More info is needed to help with the driver.