First, some background information:
Allegedly, Israel ben Eliezer Baal Shem wrote a letter to his brother in law wherein he states that on Rosh HaShanah of 5507 (1746), he spiritually ascended to the "Chamber of Moshiach" and has a conversation with the future mashiah. In the course of the conversation, the mashiah supposedly tells him that "When your wellsprings flow to the outside" (i.e. when your teachings are spread throughout the world) then he would come to redeem Israel.
Now, to answer your question:
Essentially, they are "documenting" the supposed fulfillment of the teachings of the Baal Shem Tov being spread throughout the world in the form of the Tanya. I.e. the more places and printings take place, the more the doctrines of Hasidism are spread throughout the world, the closer the coming of mashiah [supposedly] is.