All of them
When you have a Talkatoo plan, there is no limit to the number of computers on which you can install Talkatoo.You can even have all of them signed in at the same time, so if you find yourself hopping from one computer to the next, this is no problem.
The only restriction will be using Talkatoo - you can only be actively dictating on the number of computers for which you have a license. Find out more here.