Order style problem

The green square is not added by the multi-step checkout plugin, but by a CSS rule added in the “Custom CSS” option within the Medik theme settings page. You can also deactivate the multi-step checkout plugin for a moment to see that the green square is still present on the checkout page.

You can fix the image size by adding the following CSS rule to your website:

.woocommerce .woocommerce-checkout-review-order-table .product-name img {
    display: table-cell;
    float: left;
    margin-right: 20px;
    max-width: 80px;
}

You need to enable the “Validate the fields during each step” option on the “WP Admin -> WooCommerce -> WP Multi-Step Checkout” page. The option is available only in the plugin’s pro version.