Setup Step, min and max for Simple and Variable products

gistfile1.php

// Simple products
add_filter( 'woocommerce_quantity_input_args', 'jk_woocommerce_quantity_input_args', 10, 2 );
function jk_woocommerce_quantity_input_args( $args, $product ) {
    $args['input_value'] 	= 3;	// Starting value
    $args['max_value'] 		= 12; 	// Maximum value
    $args['min_value'] 		= 3;   	// Minimum value
    $args['step'] 		= 3;    // Quantity steps
    return $args;
}


// Variations
add_filter( 'woocommerce_available_variation', 'jk_woocommerce_available_variation' );
function jk_woocommerce_available_variation( $args ) {
    $args['max_qty'] = 12; 		// Maximum value (variations)
    $args['min_qty'] = 3;   	// Minimum value (variations)
    return $args;
}