The numbers are actually very good, when it is considered that the southbound am/northbound pm are likely to be busier than the reverses.
Also, the average last Sep to LCY was just under 22.8 whereas this year to STN is just over 21.2. So, despite moving to a less 'convenient' airport they have only lost 1.5 pax per flight. Assuming lower operating costs are achieved at STN, at face value this route must be more viable now than previously before receipt of PSO is even taken into account.
What would be interesting to know is how it can be quantified that this service is contributing to economic development in the Dundee area, and whether it providing local taxpayers with value for money.