I need to get % CPU currently used by my process on macOS. I expect it to be calculated this way, and it works on Windows:

(currentAppTime - lastTrackedAppTime) * 100% / (currentSysTime - lastTrackedSysTime)

lastTracked and current metrics are collected after a time interval.

Total CPU time code:

mach_msg_type_number_t count = HOST_CPU_LOAD_INFO_COUNT;
host_statistics(mach_host_self(), HOST_CPU_LOAD_INFO, (host_info_t)&cpuinfo, &count);
lastTrackedSysTime = std::accumulate(cpuinfo.cpu_ticks, cpuinfo.cpu_ticks + count, 0ULL);

Process time:

struct proc_taskinfo taskInfo;
proc_pidinfo(getpid(), PROC_PIDTASKINFO, 0, &taskInfo, sizeof(taskInfo));
lastTrackedAppTime = taskInfo.pti_total_user + taskInfo.pti_total_system;

In my code:

static uint64_t lastTrackedAppTime; // already initialized in ctor
static uint64_t lastTrackedSysTime; // already initialized in ctor

void AppMetrics::getCPU() // called every 5 seconds
{
    host_cpu_load_info_data_t cpuinfo;
    mach_msg_type_number_t count = HOST_CPU_LOAD_INFO_COUNT;
    auto hs = host_statistics(mach_host_self(), HOST_CPU_LOAD_INFO, (host_info_t)&cpuinfo, &count);
    assert(hs == KERN_SUCCESS);

    uint64_t currentSysTime = std::accumulate(cpuinfo.cpu_ticks, cpuinfo.cpu_ticks + count, 0ULL);
    uint64_t totalSysDiff = currentSysTime - lastTrackedSysTime;

    struct proc_taskinfo taskInfo;
    auto ppi = proc_pidinfo(getpid(), PROC_PIDTASKINFO, 0, &taskInfo, sizeof(taskInfo));
    assert(ppi == sizeof(taskInfo));
    
    uint64_t currentAppTime = taskInfo.pti_total_user + taskInfo.pti_total_system;
    uint64_t totalAppDiff = currentAppTime - lastTrackedAppTime;
    metrics.appCPU = totalAppDiff * 100.0 / totalSysDiff; // the value I need

    lastTrackedSysTime = currentSysTime;
    lastTrackedAppTime = currentAppTime;
}

The problem is the totalAppDiff is much bigger than totalSysDiff.

lastTrackedSysTime: 4555257262
currentSysTime: 4555261249
totalSysDiff: 3987

lastTrackedAppTime: 435637867
currentAppTime: 441909402
totalAppDiff: 6271535

How is this possible? What am I doing wrong? Am I taking the right approach at all?