WordPress at a glance
filter is not described

postmeta_form_limit filter-hook . WP 2.1.0

Filters the number of custom fields to retrieve for the drop-down in the Custom Fields meta box.

Usage

add_filter( 'postmeta_form_limit', 'filter_function_name_459' );
function filter_function_name_459( $limit ){
	// filter...

	return $limit;
}
$limit(int)
Number of custom fields to retrieve.
Default: 30

Where the hook is called

meta_form()
wp-admin/includes/template.php 623
$limit = apply_filters( 'postmeta_form_limit', 30 );

Where the hook is used (in WP core)

Does not used.