c# – Unity Coroutine unexpected behaivour

I am starting a coroutine which iterates a loop number of times and waiting a certain time between each iteration. But complation of the loop takes way more longer than the expected. Here is the code:

private IEnumerator CO_AddBladesInTime(int count, Blade blade)
    {
        var _spawnPos = blade.transform.position;
        var _counter = 0;

        var _firstTime = Time.time;
        var _calculatedTime = 0f;

        Debug.Log("entered coroutine at " + _firstTime);

        while (_counter < count)
        {
            _counter++;
            // AddNewBlade(_spawnPos, blade.Level);
            var _waitTime = bladeSpawnFreq / count;
            _calculatedTime += _waitTime;
            yield return new WaitForSeconds(_waitTime);
        }

        var _secondTime = Time.time;
        Debug.Log("exited coroutine at " + _secondTime);
        Debug.Log($"waited {_secondTime - _firstTime}");
        Debug.Log($"expected wait time {_calculatedTime}");
    }

Here is the results:

Am I missing something?