amazon CloudWatchLogs putLogEvents

hi guys i'm trying to put Log on amazon CloudWatchLogs like this:

$response2 = $amzonLoger->putLogEvents([

            'logGroupName' => 'myGroup',
            'logStreamName' => 'myStream',
            'logEvents' => [
                [
                    'timestamp' => time(),
                    'message' => 'fuck this'
                ],
            ],
            'sequenceToken' => lastToken,
        ]);
        var_dump($response2);

but always i've this response :

bject(Guzzle\Service\Resource\Model)#289 (2) { ["structure":protected]=> NULL ["data":protected]=> array(2) { ["nextSequenceToken"]=> string(56) "495401145812734324234234236420825819917076850" ["rejectedLogEventsInfo"]=> array(1) { ["tooOldLogEventEndIndex"]=> int(1) } } }

can u help me understanding what does mean ["rejectedLogEventsInfo"]=> array(1) { ["tooOldLogEventEndIndex"]=> int(1), I will be very grateful for the help.