App Engine Java API pageSize

问题

Why has google decided to ignore pageSize parameter and why the overall size of the collected items differs when using different page size? Here is an example:

Appsactivity.Activities.List  request = service.activities().list()
    .setDriveAncestorId(ancestorId)
    .setGroupingStrategy("driveUi") 
    .setSource("drive.google.com")
    .setUserId("me")
    .setPageSize(pageSize);

List<Activity> list = new LinkedList<>();
ListActivitiesResponse response = null;

do {
   response = request.execute();
   List<Activity> fetched = response.getActivities();
   System.out.println("page items: " + fetched.size());

   list.addAll(fetched);
   request.setPageToken(response.getNextPageToken());

} while (request.getPageToken() != null && request.getPageToken().length() > 0);

System.out.println("all items: " + list.size())

When I set pageSize to 100, I will get 720 items (64, 71, 60, 60, 76, 92, 87, 74, 62, 56, 18), however when I set pageSize to 5 the result set contains 810 items. Am I missing something or it's an API bug?

EDIT

I've just checked singleEvents counts by using event time as key. Few events were duplicated, however the significant difference between events count is still present, when using different pageSize.

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