@Stevoh When data is loaded first time in the Vertipaq storage the engine doesn’t have a correct estimate of how large the dictionary will be so it assigns around 1 megabyte to dictonary of each column for Power BI and Power Pivot models and 8 megabytes for SSAS. After the data is loaded the columns are compressed and then the size of the dictionary can be reduced or increased and for the exact numbers you have to save the file and re-open it.
Since you are working with a Calculated table, any modification in the code will refresh the data and will re-create the dictionary of 1 MB each time you make a change.