ByGB Blog Official 2016-10-22 814
If you see this button, press it to increase (make the pointer faster) or decrease (slow down the pointer to make it more precise) sensitivity. The new DPI (e.g., 800, 1200, etc) will appear either on the monitor or on the LCD screen of your mouse.
To decrease the DPI, keep pressing the button until the DPI number cycles back to the smallest possible number (e.g., 400 DPI).
There is no "recommended" DPI, as it is a matter of preference. Start by setting it close to the vertical resolution of your monitor. For example, if your monitor is 1920 x 1080, try setting the DPI as close as you can get it to 1080. If you want it faster or more precise, increase it from there.
Install the software that came with your mouse. If you bought a mouse labeled "gaming" or "precision," it probably came with its own software that provides the option to change the DPI (sensitivity) settings. You will be able to change the DPI in the software.
You can download the software for your mouse from the mouse manufacturer's website. Visit the website (e.g., www.logitech.com) and navigate to the product page for your specific model. Follow the download link for your operating system. If there is no software available for your mouse, you can anyway increase and decrease the pointer speed.