我想了解AWS Lambda计费持续时间与冷启动之间的关系。根据下面的Cloudwatch日志，我的应用程序花费了大约6.8秒才能启动，并且计费持续时间约为4秒，后续请求的计费持续时间较短，因为容器将处于热状态。
运行时：Java8内存：512 MB
[2018-07-20 08:49:33.455] NO-REQUEST-ID INFO c.a.s.p.i.LambdaContainerHandler - Starting Lambda Container Handler
[2018-07-20 08:49:33.666] NO-REQUEST-ID INFO c.a.s.p.i.s.AwsServletContext - 1 Spring WebApplicationInitializers detected on classpath
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2018-07-20 08:49:40.855 INFO 1 --- [ main] Application : Started Application in 6.873 seconds (JVM running for 8.156)
START RequestId: d2489678-8be9-11e8-8a6e-094e55395805 Version: $LATEST
2018-07-20 08:49:41.136 ERROR 1 --- [ main] c.a.s.p.i.s.AwsProxyHttpServletRequest : Called set character encoding to UTF-8 on a request without a content type. Character encoding will not be set
2018-07-20 08:49:44.674 INFO 1 --- [ main] c.a.s.p.internal.LambdaContainerHandler : 127.0.0.1 - [01/01/1970:00:00:00Z] "GET /employee null" 200 193 "-" "Custom User Agent String" combined
END RequestId: d2489678-8be9-11e8-8a6e-094e55395805
REPORT RequestId: d2489678-8be9-11e8-8a6e-094e55395805 Duration: 3859.12 ms Billed Duration: 3900 ms Memory Size: 512 MB Max Memory Used: 166 MB
要计算冷启动时间，我需要考虑什么时间范围？根据上述记录，将冷启动时间测量为9秒（08:49:44-08:49:33）是否正确？