Timer定时器 误差怎么会越来越大

<?php

use Workerman\Worker;
use Workerman\Timer;
require_once __DIR__ . '/vendor/autoload.php';

$task = new Worker();
// 开启多少个进程运行定时任务，注意业务是否在多进程有并发问题
$task->count = 1;
$task->onWorkerStart = function(Worker $task)
{
    // 每1秒执行一次
    $time_interval = 1;
    $start_num = time();
    Timer::add($time_interval, function() use(&$start_num)
    {
        $start_num++;
        echo time()."-----".$start_num."\r\n";
    });
};

// 运行worker
Worker::runAll();