Email Template code note working

Hello friends,

I am trying to use the Email template to send the actual contents of fields below in the email (not just the pdf attachment). The result is shows the actual code instead of the content, for example Balance due just shows up as (((formatted_balance))).
Any help would be highly appreciated. My version is v1.5.9. Have a great day a head.

Invoice #{{ $invoice->number }}

Name: {{ $invoice->client->name }}

Address: {{ $invoice->client->formatted_address }}

Your Mobile Number: {{ $invoice->client->mobile }}

Total Amount: {{ $invoice->amount->formatted_total }}

Amount Paid: {{ $invoice->amount->formatted_paid }}

Your Balance Due: {{ $invoice->amount->formatted_balance }}

You can view your invoice by clicking here:

{{ $invoice->public_url }}

From where did you get these? The correct ones are available directly besides the email template field and look like this: {{{invoice_balance}}}