Hi @Switzer-matt and thank you for asking this good question! 
As you rightly said, the reference letter is issued when a translator reaches 20000 as word count. However, the letter can be provided before reaching this threshold in very exceptional cases, for example, when a volunteer translates to a language that rarely has tasks, or when there is an urgent need for it by the volunteer who requests it. We review the requests we have on a case-by-case basis to decide the possibility of providing the letters 
As for the confirmation of contribution, it means the eligibility for adding the name, title, and email address of TWB’s Senior Community Officer, Ambra Sottile, in the volunteer’s CV/resume/job application. When Ambra is contacted by an institution the volunteer applies to work for, she can verify the contribution of the volunteer with TWB 
I hope that I could give you a clear answer, please let us know if you need more clarification on our recognition program 