OK. It is a 25 volt voltage divider so you should see a range of 0 to about 490 on the analog pin.
The voltage divider you have purchased does indeed consist of 2 resistors but has 5 (!) connections and no diagram, anyway I found this which might be the same :
You connect the output of the PNP photo cell to VCC and the "S" (I guess "Sig" on your device) connection to the arduino analog pin. The grounds are common.