How can I limit the activity feed to show 10 posts, then the load more appears?

functions.php

function limit_activities_displayed( $retval ) {
$isMob = is_numeric(strpos(strtolower($_SERVER["HTTP_USER_AGENT"]), "mobile"));
if ($isMob) {
$retval['per_page'] = 15;
}
else {
$retval['per_page'] = 5;
}
return $retval;
}
add_filter( 'bp_after_has_activities_parse_args', 'limit_activities_displayed' );