I am not very familiar with the software since I only downloaded it yesterday, but from what I have read and see, you can choose the starting number, but then the software counter takes over. You can also add a number prefix (optional), but that is it. Good luck getting support on this product. I am considering buying it, but with the complete lack of support for the most basic of questions, I am thinking that there is no point in even trying to use this software. The reviews I have read are also very negative regarding support. Even the platinum support plan only gives you a few e-mail and I believe 2 phone calls and if you don't use them, 3 months later you are out because they expire. This is a real load of crap! It is a shame because the Express Invoice product itself seems very flexible and easy to use with an attractive price, but if the developer is not going to properly support it then what is the point of getting it?