The PDH_STATISTICS structure is used to return the statistics of the values in an array of raw counters managed by the application program. The format of the data in the PDH_FMT_COUNTERVALUE structure is described in the dwFormat member.
typedef struct _PDH_STATISTICS {
    DWORD                   dwFormat;
    DWORD                   count;
    PDH_FMT_COUNTERVALUE    min;
    PDH_FMT_COUNTERVALUE    max;
    PDH_FMT_COUNTERVALUE    mean;
} PDH_STATISTICS, *PPDH_STATISTICS;
 Performance Data Helper Overview, Performance Data Structures, PdhComputeCounterStatistics, PDH_FMT_COUNTERVALUE