WooCommerce, Get Setting Value

Creating a simple payment gateway. I’ve created some settings fields, and am wondering how can I get these values later?

public function init_form_fields() {
		$this->form_fields = array(
			'min_balance' => array(
				'title'		=> __( 'Minimum Checkout Balance', 'plugin_name' ),
				'type'		=> 'text',
				'desc_tip'	=> __( 'Default 0.', 'plugin_name' ),
				'default'	=> __( '0', 'plugin_name' ),
				'css'		=> 'max-width:350px;'
			)
		);
	}

I’ve found:
$string = WC_Admin_Settings::get_option( $option_name, $default );
but am not sure the correct syntax, or even if that’s the correct direction. Any suggestions much appreciated!