How to get CPM value from the RadSens Geiger counter board with RadSensBoard library

CountsPerMinute.h

#ifndef __COUNTS_PER_MINUTE_H__
#define __COUNTS_PER_MINUTE_H__

class CountsPerMinute
{
    int m_currentCpm;
    int m_maximumCpm;
    int m_intervalsPerMinute;
    int* m_intervalCounts;
    int m_currentInterval;
    int m_initialInterval;

public:

    CountsPerMinute() { }

    void init(int intervalsPerMinute)
    {
        this->m_currentCpm = 0;
        this->m_maximumCpm = 0;
        this->m_intervalsPerMinute = intervalsPerMinute;
        this->m_intervalCounts = new int[this->m_intervalsPerMinute];
        for (int i = 0; i < this->m_intervalsPerMinute; i++)
        {
            this->m_intervalCounts[i] = 0;
        }
        this->m_currentInterval = 0;
        this->m_initialInterval = 0;
    }

    bool isReady() { return this->m_initialInterval >= this->m_intervalsPerMinute; }

    int getCurrentCpm() { return this->m_currentCpm; }

    int getMaximumCpm() { return this->m_maximumCpm; }

    void add(int count)
    {
        if (this->isReady())
        {
            this->m_currentCpm = this->m_currentCpm - this->m_intervalCounts[m_currentInterval] + count;
        }
        else
        {
            this->m_currentCpm += count;
            this->m_initialInterval++;
        }

        if (this->m_maximumCpm < this->m_currentCpm)
        {
            this->m_maximumCpm = this->m_currentCpm;
        }

        this->m_intervalCounts[m_currentInterval] = count;

        m_currentInterval++;
        if (m_currentInterval >= m_intervalsPerMinute)
        {
            m_currentInterval = 0;
        }
    }

};

#endif // __COUNTS_PER_MINUTE_H__

main.cpp

// RadSensBoard library:
// https://github.com/vurdalakov/radsensboard

#include <Arduino.h>
#include <RadSensBoard.h>
#include <CountsPerMinute.h>

#define SECONDS_PER_INTERVAL 5

RadSensBoard radSensBoard;
CountsPerMinute cpm;

void setup()
{
    radSensBoard.init();
    cpm.init(60 / SECONDS_PER_INTERVAL);
}

void loop()
{
    int counts = radSensBoard.getPulseCount();
    radSensBoard.resetPulseCount();

    cpm.add(counts);

    if (cpm.isReady())
    {
        serial.print("CPM:     ");
        serial.println(cpm.getCurrentCpm());
        serial.print("Max CPM: ");
        serial.println(cpm.getMaximumCpm());
    }

    delay(SECONDS_PER_INTERVAL * 1000);
}