Hay all i got a 10mm error here

Right its in the height of U1 and U2. The distance between the top of br1 and tr1 is 305mm. But if you work out the height of U1 using the measurements in the back of the book it comes out at 315. With a hypotenuse of 345mm and an angle of 24' gives a height of 315.
Anyone else found this?