I really really hate this machine. I don't understand it, I don't know how to set up Bluetooth, I find the instructions so small and the print so faded, I can't read anything. And I have no idea what the control vials are for. I don't know what "in vitro" means. What an awful experience. I wish I just got a simple machine AND a simple explanation of how to calculate the GKI. Your explanations are conflicting, I have no idea what you are talking about. I received this product with some kind of receipt that didn't even show he amount of payment. I will be calling for a refund, and I do not recommend this product