How to get correctly the percent of used CPU per process

I'm trying to get the percent of used CPU per process on windows with Qt/C++. Firstly i get a list of running processes and after, for each process i try to get the used CPU, for most process the result looks valid (they match with task manager in windows), but with the AIDA64 process (that is running a CPU stress test in background), i got strange values like 312% what is wrong with my c++ code?

    sigar_t *sigarproclist;

    sigar_proc_list_t proclist;

    sigar_open(&sigarproclist);

    sigar_proc_list_get(sigarproclist, &proclist);

    for (size_t i = 0; i < proclist.number; i++)

    {

        sigar_proc_cpu_t cpu;

        int status1 = sigar_proc_cpu_get(sigarproclist, proclist.data[i], &cpu);

        if (status1 == SIGAR_OK)

        {

            Sleep(50);

            int status2 = sigar_proc_cpu_get(sigarproclist, proclist.data[i], &cpu);

            if (status2 == SIGAR_OK)

            {

                sigar_proc_state_t procstate;

                sigar_proc_state_get(sigarproclist, proclist.data[i], &procstate);

                qDebug() << procstate.name << cpu.percent * 100 << "%";

            }

        }

    }

    sigar_close(sigarproclist);