shortly here means soon

The sentence "We'll have your results ready shortly" means that the person or organization is in the process of preparing your results and they will be available or ready for you in a short period of time. It doesn't necessarily mean "immediately," but rather that it won't take too long. "Shortly" is a more flexible term that could mean a few minutes, hours, or perhaps even a day or two, depending on the context.

It means "we will possess your results soon, and they will be ready for you to see".

The results will be ready...soon. In a short time. Maybe not immediately but you won't have to wait long. But 'shortly' is an indefinite term. A minute? An hour? A day? Longer? It depends on the situation. 'prepare' is not quite the right verb. They may already be prepared. Perhaps they just have not been sent out yet.

It just means very soon.