The docs specify the following:
max_id (int, optional) - The checkin ID that you want the results to start with
min_id (int, optional) - Returns only checkins that are newer than this value
limit (int, optional) - The number of results to return, max of 25, default is 25
While the code passes along:
$args = array(
'since' => $since,
'offset' => $offset,
'limit' => $limit,
);