There is not an easy way to do this. You would need to do a query for each of the values and count the posts returned. For example
// status completed
$args = array(
'post_type' => 'your post type',
'post_status' => 'publish', // or whatever
// other WP_Query arguments as needed
'fields' => 'ids', // return only post IDs, since we just need to get a count
'meta_query' => array(
array(
'key' => 'your field name',
'value' => 'complete'
)
)
);
$results = new WP_Query($args);
$completed = count($results->posts);