"Which.co.uk" power converter: it's wrong isn't it?

[LotusOmega375D]

Just googled this to cross reference some BHP and PS values. Am I stupid or does it give you the wrong answer? The text says 1.0 PS = 0.986 BHP, but if you type in say 100 BHP it converts this to 99 PS rather than 101 PS. I would have thought that such an august organisation as Which would have got this right.

http://www.which.co.uk/cars/driving/driver-tools/p...