Question about Chapter07 /02b_stack_cas.C

[qdztxc]

For push and pop function.

void push(const T& v) {
    // Reserve the slot for the new object by advancing the producer count.
    counts_t n = n_.load(std::memory_order_relaxed);
    if (n.pc_ == cap_) abort();
    int i = 0;
    while (!n.equal(n_) || !n_.compare_exchange_weak(n, {n.pc_ + 1, n.cc_}, std::memory_order_acquire, std::memory_order_relaxed)) {
        if (n.pc_ == cap_) abort();
        nanosleep(i);
    };
    // Producer count advanced, slot n.pc_ + 1 is ours.
    ++n.pc_;
    new (&s_[n.pc_]) T(v);

    // Advance the consumer count to match.
    if (!n_.compare_exchange_strong(n, {n.pc_, n.cc_ + 1}, std::memory_order_release, std::memory_order_relaxed)) abort();
}
std::optional<T> pop() {
    // Decrement the consumer count.
    counts_t n = n_.load(std::memory_order_relaxed);
    if (n.cc_ == 0) return std::optional<T>(std::nullopt);
    int i = 0;
    while (!n.equal(n_) || !n_.compare_exchange_weak(n, {n.pc_, n.cc_ - 1}, std::memory_order_acquire, std::memory_order_relaxed)) { 
        if (n.cc_ == 0) return std::optional<T>(std::nullopt);
        nanosleep(i);
    };
    // Consumer count decremented, slot n.cc_ - 1 is ours.
    --n.cc_;
    std::optional<T> res(std::move(s_[n.pc_]));
    s_[n.pc_].~T();

    // Decrement the producer count to match.
    if (!n_.compare_exchange_strong(n, {n.pc_ - 1, n.cc_}, std::memory_order_release, std::memory_order_relaxed)) abort();
    return res;
}

in
while (!n.equal(n_) || !n_.compare_exchange_weak(n, {n.pc_ + 1, n.cc_}, std::memory_order_acquire, std::memory_order_relaxed)) {
n.pc_ is already updated to n.pc_ + 1.
while (!n.equal(n_) || !n_.compare_exchange_weak(n, {n.pc_, n.cc_ - 1}, std::memory_order_acquire, std::memory_order_relaxed)) {
n.cc_ is already updated to n.cc_ -1.
why n.pc_ and n.cc_ updated again in the following:
++n.pc_;
--n.cc_;
are these update duplicate?