In QR section only, there is a computer calculator that you can only use by clicking your mouse (you can't use the keyboard to type in the numbers). Lagging of the calculator I think depends on the computers at the testing centers, which vary. I've heard of some centers with older computers and some with newer computers. I planned to NOT use the calculator while studying for QR, but fortunately, the calculator at my center was not too laggy, so I ended up using it, which helped quite a bit actually.
