In statistical objects In MXMetricPayload histogrammedTimeToFirstDrawKey start times not equal applicationExitMetrics exit

In statistical objects In MXMetricPayload histogrammedTimeToFirstDrawKey start times not equal applicationExitMetrics exit：

case1:

       "applicationExitMetrics": {
            "backgroundExitData": {
                "cumulativeNormalAppExitCount": 3,
                "cumulativeMemoryPressureExitCount": 4
            },
            "foregroundExitData": {
                "cumulativeMemoryResourceLimitExitCount": 3
            }
        },
        "applicationLaunchMetrics": {
            "histogrammedTimeToFirstDrawKey": {
                "histogramNumBuckets": 14,
                "histogramValue": {
                    "10": {
                        "bucketCount": 1,
                        "bucketStart": "1740 ms",
                        "bucketEnd": "1749 ms"
                    },
                    "2": {
                        "bucketCount": 1,
                        "bucketStart": "1440 ms",
                        "bucketEnd": "1449 ms"
                    },
                    "3": {
                        "bucketCount": 2,
                        "bucketStart": "1490 ms",
                        "bucketEnd": "1499 ms"
                    },
                    "11": {
                        "bucketCount": 1,
                        "bucketStart": "1780 ms",
                        "bucketEnd": "1789 ms"
                    },
                    "4": {
                        "bucketCount": 1,
                        "bucketStart": "1500 ms",
                        "bucketEnd": "1509 ms"
                    },
                    "5": {
                        "bucketCount": 1,
                        "bucketStart": "1580 ms",
                        "bucketEnd": "1589 ms"
                    },
                    "12": {
                        "bucketCount": 1,
                        "bucketStart": "1860 ms",
                        "bucketEnd": "1869 ms"
                    },
                    "6": {
                        "bucketCount": 1,
                        "bucketStart": "1620 ms",
                        "bucketEnd": "1629 ms"
                    },
                    "13": {
                        "bucketCount": 1,
                        "bucketStart": "1990 ms",
                        "bucketEnd": "1999 ms"
                    },
                    "7": {
                        "bucketCount": 1,
                        "bucketStart": "1650 ms",
                        "bucketEnd": "1659 ms"
                    },
                    "0": {
                        "bucketCount": 1,
                        "bucketStart": "1400 ms",
                        "bucketEnd": "1409 ms"
                    },
                    "8": {
                        "bucketCount": 1,
                        "bucketStart": "1660 ms",
                        "bucketEnd": "1669 ms"
                    },
                    "1": {
                        "bucketCount": 1,
                        "bucketStart": "1430 ms",
                        "bucketEnd": "1439 ms"
                    },
                    "9": {
                        "bucketCount": 1,
                        "bucketStart": "1730 ms",
                        "bucketEnd": "1739 ms"
                    }
                }
            },

In this Case the app cold started 15 times, but quit only 10 times， why？？

case2:

      "applicationExitMetrics": {
            "backgroundExitData": {
                "cumulativeMemoryPressureExitCount": 1
            },
            "foregroundExitData": {
                "cumulativeMemoryResourceLimitExitCount": 3,
                "cumulativeNormalAppExitCount": 1
            }
        },
 
        "applicationLaunchMetrics": {
            "histogrammedTimeToFirstDrawKey": {
                "histogramNumBuckets": 3,
                "histogramValue": {
                    "0": {
                        "bucketCount": 1,
                        "bucketStart": "1490 ms",
                        "bucketEnd": "1499 ms"
                    },
                    "1": {
                        "bucketCount": 1,
                        "bucketStart": "1680 ms",
                        "bucketEnd": "1689 ms"
                    },
                    "2": {
                        "bucketCount": 1,
                        "bucketStart": "1880 ms",
                        "bucketEnd": "1889 ms"
                    }
                }
            },

The app cold started 3 times, but quit unexpectedly reached 5 times， why？？？