12 units of Dysport in each side of masseter to slim jaw (24 units total). Isn't that equivalent to 4 units of Botox per side?

Hello and thanks.This is a good start. You can always have more injected later. Unless you have serious masseter hypertrophy, I would not disagree with this starting dose. Higher doses can be associated with trouble swallowing, so I think you're injector did right. Share your concerns with your injector and follow up at 2 weeks.Best wishes, Dr. ALDO :)

Thank you for the question.   I think you are correct, and that 12 units per side is not close to enough.  I usually treat with at least 25 units per side, but have gone up to 40 units per side of Botox (roughly equal to 75-120 units Dysport each side).  Good luck! 

Thank you for the excellent question. 
In general terms, Dysport 3U = Botox 1U.  It is best to confirm how your injector diluted the Dysport.  Dysport 12U per masseter is insufficient to produce atrophy, or slimming, of the masseter.  In my experience, it requires a minimum of Botox 20-30 U per masseter to produce a slimmer face.  Once achieved, the results tend to last upto a year.
Since many clients switch injectors for a variety of reasons, we avoid confusion by advertising a Dysport Injected Unit as containing 3 Vial Units.  In other words, Dysport is diluted at 3U per 0.01 cc of solution compared with Botox which is diluted at 1U per 0.01 cc of solution.  In this manner, clients can easily understand how many units produced the desired result whether it's Botox or Dysport.
Dysport is an excellent neuromodulator and frequently preferred by our clients.  
I hope this answer provides clarity and sufficiently answers your question.