This map depicts the United Baltic Duchy, a state which was proposed but never truly saw the light of day. Its creation was proposed by the Baltic German and Russian aristocracy towards the end of the Great War, and it was to be in personal union with the Crown of Prussia. The Kaiser declined the proposal historically for a variety of reasons, greatest of which was probably the fact that Germany wasn't exactly doing all that well in 1918, with the Allies gaining ground and the German Revolution making a mess of things at home.
In any case, in this universe - which I may or may not chose to develop further depending on how well this map is received - things went well for the German Empire in the Great War, and the Kaiser was in a position to accept the proposal from the Baltic nobles. This resulted in the creation of the planned United Baltic Duchy, with Adolf Friedrich, Duke of Mecklenburg, as the first head of state. (Under the Kaiser, of course.)
The divisions are based on what Wikipedia tells me is how they were going to organize this new United Duchy, with 7 cantons/districts total. Those seven cantons were to be Courland (and Semigallia), Latgallia, South Livonia, North Livonia, Estonia, Ösel and Riga.