As a follow-up question, I would ask how the training simulators are sold. Are you hired by a company or school to provide training simulation (i.e. work-for-hire fees?) or do you make a product and sell it? If the former, no royalties are owed, and you only need a seat license per developer. You mention that your products contain hardware and software, but I’m not sure how it is sold.
I can also add that, unfortunately, for the time being we are not able to license UE4 by subscription in China, but we hope to have that resolved in the near future.