Add this into functions.php pf your child theme.

// Simple products
add_filter( ‘woocommerce_quantity_input_args’, ‘jk_woocommerce_quantity_input_args’, 10, 2 );

function jk_woocommerce_quantity_input_args( $args, $product ) {
if ( is_singular( ‘product’ ) ) {
$args[‘input_value’] = 2; // Starting value (we only want to affect product pages, not cart)
}
$args[‘max_value’] = 80; // Maximum value
$args[‘min_value’] = 2; // Minimum value
$args[‘step’] = 2; // Quantity steps
return $args;
}

// Variations
add_filter( ‘woocommerce_available_variation’, ‘jk_woocommerce_available_variation’ );

function jk_woocommerce_available_variation( $args ) {
$args[‘max_qty’] = 80; // Maximum value (variations)
$args[‘min_qty’] = 2; // Minimum value (variations)
return $args;
}