Time using the Computer is counted as any time in which there was mouse or keyboard activity within the last 30 seconds. Time using the Mouse is counted as any time in which there was a mouse click or mouse movement within the last 5 seconds. Time using the Keyboard is counted as any time in which there was keypress within the last 5 seconds. Why different threshols for computer usage and mouse/keyboard usage? Computer usage has a higher threshold because we are wanting to measure your time spent at the computer, not just your time using the mouse and keyboard. You may spend periods not actively using the mouse or keyboard, but still with a static posture at the computer (e.g. reading from the VDU.) For example, it is quite possible you could spend 30 seconds without moving the mouse or typing a keystroke, but still be sitting at the computer, perhaps reading something from the computer screen. However, it is unlikely that you could hold your hand still on the mouse for 30 seconds without making any slight movements of the mouse.