Don't stress about right/wrong on cube counting practice, just learn how to identify quickly what cubes are 1,2,3,4,5 sides showing so you don't have to actually count each side of a cube. The more problems you do, the quicker you get at tallying the amount of sides there are and you will get to a point where you can do all the cubes in a very short time.
On the real DAT the images are very simple and if you can quickly tally the cubes you can blow through the section. Between hole punch, cube counting and angles, if you can do these all in approx 5 minutes each, it will give you plenty of time for the harder sections.
So sorry, long answer, but main point is don't stress about cube questions you cant figure out the given answer. Just keep practicing and get quick!