Box Sign - template with tags

Hi, I am working on Box sign document using tags by following the below document. https://support.box.com/hc/en-us/articles/4404085855251-Creating-templates-using-tags. When I send the document to myself for testing after putting the pre filled tags it doesn't render the format what you mentioned in the document rather it appears like this only '[[t|0   Customer Name   ]]'. Where I am looking forward to achieve as per the screenshot I put below. Does pre filled tags also needs API? Thanks in advance.