Checkboxes Count = Number Field

add_action('acf/save_post', 'count_titles');

function count_titles($post_id)
{
	$post_id = "teams";

	// ACF teams field values.
	$sixteenRegion = get_field('16th_region_title_year_won', 'teams');

	// Calculate total pets.
	$calcSixteen = count($sixteenRegion);

	// Update ACF field for total_pets.
	update_field('total_16th_region_titles', $calcSixteen, $post_id);
}

add_filter('acf/format_value/type=number', 'format_numbers');

function format_numbers($value, $post_id, $field)
{
	$value = number_format($value);
	
	return $value;
}

I know this code is probably very wrong. I’ve tried piecing it together from other researching common threads but I can’t seem to get it to work the way I want it.

I am trying to autopopulate the number field based on how many checkboxes are checked in another field. So for example, if the checkbox field has 5 of the 16 checkboxes checked. Then “5” should be populated in the number field above. I keep getting an error and it’s probably from just a dumb syntax error or just plain wrong code. IAny help would be great!