Microbit LED's won't turn on with my code, or if statement dosen't work as needed

micro:bit
1

My code wont work. I’m trying to make it so that how big of a light level will display on the led. The smallest value is [0,0] in the leds, so when there is no light I want the [0,0] led to show up, then it goes up progressing.
I used Python.

Old_Plot = [0,0]

PlotX = Old_Plot[0]
PlotY = Old_Plot[1]

def Functionality():
    global PlotX, PlotY, Old_Plot
    reading = input.light_level()
    final_reading = Math.round(abs(reading / 25) * 2.5) # Nei, dette er ikke fra google, abs står får "Absolute Value" det gjør negative tall om til positive, so eks: -3 blir til 3
    
    if not final_reading == 0:
        final_reading -= 1 # Fordi datamaskiner starter alltid på 0

    if final_reading > 25:
        final_reading = 25

    # print(str(final_reading))


    PlotX = final_reading / 5
    
    if PlotX >= (PlotY * 5) + 1:
        PlotY += 1
        PlotX = 0
    print(PlotX)
    print(PlotY)

    led.unplot(Old_Plot[0], Old_Plot[1])
    led.plot(PlotX, PlotY)
    Old_Plot = [PlotX,PlotY]
    

while True:
    Functionality()
2

Microbit’s use 0 to 4 not 1 to 5. because computers like 0