Create a custom set of column number selections for the Post Grid element.

functions.php

<?php
/**
 * Create a custom set of column number 
 * selections for the Post Grid element.
 */
function my_elements( $elements ) {

	$elements['post_grid']['options']['columns']['options'] = array(
		'1' => __( '1 Column' ),
		'2' => __( '2 Column' ),
		'3' => __( '3 Column' ),
		'4' => __( '4 Column' ),
		'5' => __( '5 Column' )
	);

	return $elements;

}
add_filter( 'themeblvd_elements', 'my_elements' );