The fact that you didn’t understand such a normal clearance says more about you than the controller. I don’t mean to offend you just trying to help you understand. It’s not an unusual scenario as you titled this thread, it’s a daily occurrence.
The answer from the controller sounds to me like she was trying to help you understand the clearance. It sounds like an explanation of how climb via works not an explanation of her specific clearance, just based on what you wrote, obviously I wasn’t there.
Just one mans opinion. I have similar confusion when I fly in Europe and Asia , there are so many different ways of phrasing these kinds of clearances around the world. My company (Delta) gives us copious notes on each specific airport and clearances that we might get that we haven’t heard before. I find myself often asking for clarification on altitude clearances in other parts of the world.
To to be clear though, the way that clearance was issued is a normal procedure in the USA and it means climb via until reaching 15000 and then stop climbing.
Hope that helps.