Additional documents for not filing during the initial registration period. This is what they have mentioned in the website and I received the same thing in mail.

To qualify to file your initial TPS application late, you must meet at least one of the late initial filing conditions below:

During either the initial registration period of your country’s designation or during any subsequent initial registration period if your country was re-designated you met one of the following conditions, and you register while the condition still exists or within a 60-day period immediately following the expiration or termination of such condition
You were a nonimmigrant, were granted voluntary departure status, or any relief from removal
You had an application for change of status, adjustment of status, asylum, voluntary departure, or any relief from removal which was pending or subject to further review or appeal
You were a parolee or had a pending request for re-parole
You are a spouse of an individual who is currently eligible for TPS