Re the OP I find the charging policy unusual unless the nominal rate is set low to be an enticement and needs to be jacked up by 16%.
Our school charges for brakes off to brakes on either a dual or solo rate as appropriate as Brakes off to brakes on is what goes in the logbook.
We also record tacho time and airborne time and generally tacho time and airborne time usually come close to brakes off to brakes on plus 10. it varies a bit depending on the home runway in use and the proficiency of the pilot/student.
The tip for all prospective students is do a proper comparison of cost per logbook hour. This includes any additional bits for briefing / debriefing/ fuel surcharges etc.
The other potential gotcha is with landings. Is it one price for the whole detail irrespective of the number of landings per detail or do you pay for each landing /touch and go? It can make a considerable difference to the overall cost for each lesson.
Lack of transparency and "sweetheart" rates too good to be true are a common problem in the flight training field.
Don't be afraid to ask for sample invoices.