Queues must be defined as array

'supervisor-1' => [
    'connection' => 'redis',
    'queue' => ['queue1', 'queue2'],
    'balance' => 'simple',
    'processes' => 10,
    'tries' => 3,
],

Also you can define multiple supervisors

'supervisor-1' => [
    'connection' => 'redis',
    'queue' => ['queue1', 'queue2'],
    'balance' => 'simple',
    'processes' => 10,
    'tries' => 3,
],

'supervisor-2' => [
    'connection' => 'redis',
    'queue' => ['queue3', 'queue4'],
    'balance' => 'simple',
    'processes' => 10,
    'tries' => 3,
],

for more informations, you can read this article here