What is the importance of the two letters that came to Gertas apartment at the beginning of chapter 15 in a night divided

Itscome to our attention that someone has been taking extra supply out of the supply cabinet for some time now and this is not allowed the officer manager says if this continues to happen we will have to put up security cameras this will come out of the office budget there for our paychecks make sure that you're only using me budget for the for your department