What does the 'other' subscription tag mean?

Northbeam's subscription analytics works using order tags from your e-commerce provider

Northbeam's subscription analytics works using order tags from your ecommerce provider to then tag those orders and attribute them across their system. 

We offer three subscription categories: first-time subscription order, recurring subscription order, and other. Other means Northbeam is unable to identify if it is a first-time or recurring subscription order.  

This could be because older versions of subscription software didn't indicate what if orders were first-time versus recurring, so Northbeam will be unable to label that.