Led controll with slider pot

#include <Wire.h>
#include <Adafruit_ADS1X15.h>
#include "FastLED.h"
#include "Leds.h"

#define MAX_SLIDE_POT_ANALOG_READ_VALUE 2000

Adafruit_ADS1115 ads;
int16_t adc0;
int16_t adc1;

int slider_a_start = 0;
int slider_a_end = 12;

int slider_b_start = 13;
int slider_b_end = 25;

void setup() {
  Serial.begin(115200);
  Wire.begin();

  ads.begin();

  FastLED.addLeds<WS2812B, PIN_LEDS, GRB>(rgb_led, NUM_LEDS);
  FastLED.setBrightness(BRIGHTNESS_LEDS);
}

void loop() {
  adc0 = ads.readADC_SingleEnded(0);
  adc1 = ads.readADC_SingleEnded(1);
  int16_t adc_test = adc0 / 100;
  Serial.print("Analog input pin 0: ");
  Serial.println(adc0);
  Serial.print("Analog input pin 1: ");
  Serial.println(adc1);

  int num_leds_switchedon_a = map(adc0, 0, MAX_SLIDE_POT_ANALOG_READ_VALUE, slider_a_start, slider_a_end);
  int num_leds_switchedon_b = map(adc1, 0, MAX_SLIDE_POT_ANALOG_READ_VALUE, slider_b_start, slider_b_end);
  int sliderval_a = calcSlidersForLEDS(num_leds_switchedon_a, 4, 0);
  int sliderval_b = calcSlidersForLEDS(num_leds_switchedon_b, 4, 15);

  Serial.println(sliderval_a);
  Serial.println(num_leds_switchedon_a);

  for (int i = slider_a_start; i < num_leds_switchedon_a; ++i) {
    rgb_led[i] = LED_COLOR_GREEN;
  }

  for (int i = num_leds_switchedon_a; i < NUM_LEDS; ++i) {
    rgb_led[i] = CRGB::Black;
  }

  for (int i = slider_b_start; i < num_leds_switchedon_b ; ++i) {
    rgb_led[i] = LED_COLOR_GREEN;
  }

  for (int i = num_leds_switchedon_b ; i < NUM_LEDS; ++i) {
    rgb_led[i] = CRGB::Black;
  }

  FastLED.show();

  delay(50);
}


// *********** Leds.h ************* //

// Defines
#define NUM_LEDS 48
#define PIN_LEDS 13
#define LED_COLOR_GREEN CRGB::Green
#define LED_COLOR_ORANGE CRGB::Orange
#define LED_COLOR_RED CRGB::Red
#define BRIGHTNESS_LEDS 50  // ValueRange = 0-255

// Setup LED's
CRGB rgb_led[NUM_LEDS];  // color array of the LED RGB strip

// Calculate Sliders to LED's
int calcSlidersForLEDS(int slider, int divided, int pos) {
  if (pos == 0) {
    return (slider / divided);
  } else {
    return (slider / divided) + pos;
  }
}