POT is one of those commands you have to experiment with depending on your values of R and C.

For example, in one design, to get a span of approximately 0-255 into my variable I use...

POT WLTimer,95,DataA

For this particular Scale value, I was using a 10K preset and a 100nF Capacitor (the same ultra-cheapo Y5V dieletric Capacitors that are used for decoupling the PIC).