Compare custom field values

Instead of storing your values as “5 hours 13 minutes” instead store them as timestamps, e.g. 5:13 for 5h 13m

This way you can use the date/time comparator operations to answer questions

E.g. to get items under 5 hours and 30 minutes:

$args = [
    ...
    'meta_query' => [
        [
            'meta_key'     => 'time',
            'meta_value'   => date( "5:30" ),
            'meta_compare' => '<',
            'type'         => 'TIME',
        ],
    ],
];
$query = new WP_Query( $args );

This will match a 3 hour post, or a 4:20 post, or a 5h 29min post.

You may need to add :00 for the seconds on to the end of all code and values.

For display you can use human_readable_duration. This will include the seconds though, but the function is very simple so copying and modifying it to your requirements should be straight forward.