Count distinct is a measure (aggregate function). When the measure is used in the total row, it is not summing the distinct count values about but is calculating the function in the context of all the table data. Without seeing the data I would make the assumption that there are 85 distinct values between those 4 months. March, for example, happens to contain 83 of 85 of those values.
If you want a sum of the values above, you can use SUMX.
Count of ProjectName =
VALUES ( 'put table name here'[MonthNameShort] ),
CALCULATE ( DISTINCTCOUNT ( 'put table name here'[ProjectName] ) )
Comparison in Power BI: