Vaadin Flow Grid with lazy loading fetches too many rows

Question

I configured a Vaadin Flow Grid with:

grid.setPageSize(20);

grid.setItems(q -> {
          
Page<UserSummary> page = userService.findUsers(
    dataViewFilter.getName(),
    dataViewFilter.getEmail(),
    q.getPage(), q.getPageSize());

    return page.getContent().stream();
});

In my test environment, I have 100 users in the database.

During the initial page load, the Grid fetches 80 users through 4 service method calls with the specified page/size:

0 : 20
1 : 20
2 : 20
3 : 20

I can see only 15-18 rows on the screen. To see others I have to scroll. How can I prevent the Grid from fetching so many rows at once? I believe having 20 or 40 records fetched from the db should suffice for the initial screen. What am I doing wrong and how to fix it? Thanks.