Hi, and welcome! I'm gonna jump in here because this is classic case of mis-informed and hopefully me and some others can help you out here
Your yorkie being over 6 lbs is not what some consider a "teacup". I for one don't use the term to describe any yorkie, they're just tiny if they are under 4 lbs in my opinion. I am glad that your girl isn't a so-called teacup because it would be hard on her to breed if so. You said she is 4 yrs old, that isn't bad at all. I would like to say that you should just do your research, which you will find tons of here and lots of nice folks who will be willing to help you to learn what you are in store for. Do you have a pic of your female you would like to breed? Have you weighed out her faulty qualities over her good one's before deciding to breed her? Have you checked out the background on the potential stud? I know questions questions but we all just want what is best for you and for her. There is no way for me or anyone to tell you how many puppies to expect. That is determined by how many eggs she produces and the time span in which she is bred to the male...