why export the metric two times ?

[ylywyn]

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  why export the metric two times ? the log time: 2021-03-18 11:35:24, timeBucket: 202103181134, 202103181135

`2021-03-18 11:35:24,488 - org.apache.skywalking.oap.server.exporter.provider.http.HttpExporter - 71 [pool-6-thread-1] INFO [] - MetricsMetaInfo{metricsName='service_sla', scope=1, id='YXV0by1jbG91ZC1tb25pdG9y.1'} 202103181134

2021-03-18 11:35:24,489 - org.apache.skywalking.oap.server.exporter.provider.http.HttpExporter - 71 [pool-6-thread-1] INFO [] - MetricsMetaInfo{metricsName='service_sla', scope=1, id='YXV0by1jbG91ZC1tb25pdG9y.1'} 202103181135`