Post_per_page => 1 Returning more than one post

So I have no idea why this is happening. I have a custom post type called event. I want to just show the most upcoming event on the home page. For some reason, all the events that I have entered to test are being shown. Here is the query that I am using.

<?php
$today = date('Ymd',strtotime("now"));
$future = date('Ymd',strtotime("+12 months"));
$upcoming_args = array (
	'post_type' => 'event',
	'post_per_page' => 1,
	'meta_key' => 'date',
	'meta_compare' => 'BETWEEN',
	'meta_type' => 'numeric',
	'meta_value' => array($today, $future),
	'orderby' => 'meta_value_num',
	'order' => 'ASC'
);

$upcoming_query = new WP_Query($upcoming_args);

if($upcoming_query->have_posts() ):

	while($upcoming_query->have_posts() ) : $upcoming_query->the_post(); ?>

		<?php
		$date = get_field('date');
		$starting_time = get_field('starting_time');
		$ending_time = get_field('ending_time');
		?>

		<div class="col-sm-4">
		<a href="<?php the_permalink(); ?>">

			<div class="homepage-well event align_center">
				<h2><?php the_title(); ?></h2>
				<h3><?php echo $date; ?></h3>
				<h3><?php echo $starting_time ?></h3>
			</div>

		</a>
		</div>

	<?php endwhile; ?>
	<?php wp_reset_postdata(); ?>
<?php else: ?>
	<p class="lead">No events</p>
<?php endif; ?>