I found out the problem. I have over 8000 users in my DB. I wanted to take them all by

$arrayOfParameters = array(
    'search' => array(
        'queryString' => '*',
        'numberOfResults' => 1000,
        'startRow' => 0, // Then 1000...2000...3000
        'accurateTotal' => true
    ),
);
$client->searchUsersByQuery($arrayOfParameters);

And when i go with this logic of increasing the startRow value then i see:

int(26)
int(787)
int(353)
int(806)
int(596)
int(435)
int(997)
int(23)
int(5023)

This is call by call (in foreach) count result how many users i get (I always increase startRow by 1000). So why on the end i get different numbers of users? If once is possible to get 1000 why not always?

Does anyone had this problem before?