Its about 10-15 dots, arranged in a circle with arrows pointing in a clockwise direction. You will be given a practice exercise demonstrating the errors you will have to check for part 1.
In part two, there are two rows of shapes, again it is demonstrated how these will need to be either selected as having errors or not. I was thrown a bit when it changed to high demand and lost a few until I got the hang of it, after you get going though you find it quite easy, the practice paper does prepare you for this if you have had a good go at it.
Part 3 is a combination of the two earlier tests. The primary task is the 1st part(the left hand side) make sure you dont miss any errors for it. The right hand side shapes can be checked in between checking the track if you time it right.
Best of luck, Im sure you'll discover its not impossible to do, I personally had a few slip ups but if I could do it again Im sure I'd make a better go of it.