Waterstone's are currently selling a book on their online store called
"IMPROVE YOUR MATHS"
by a chap called Alan Graham.
Now Mr. Fact, being a pedantic sort of chap, was rather taken with the "40% off" sticker - until he checked the actual price of £49.99
The money-off price being quoted was £24.99 -" £25.00 OFF" as the blurb added for good measure.
I can only assume that whoever was writing the stuff hadn't looked at the book.
40% off would give a price of £29.99 ( or thereby) NOT £24.99.
£25 off gives you a price of £24.99 right enough - but sadly a discount of 50.01% ( or thereby.)
And it would have looked so much better as " MORE than 50% OFF!"