You can have Nicestats on all the devices you use.
If you have 2 PCs for the same purpose (for example, “personal use”), with the same operating system (for example, Windows) and install Nicestats on both in the same browser (for example, Chrome), it counts as one device. In this case, you would receive Korus for having Nicestats set up in Chrome on a personal Windows PC.
Having PCs with the same characteristics (purpose and browser) means we have no way of differentiating from which device the data is sent. That's why they are shown grouped into one.