Here's a quick explanation of what the marks mean.
10
10 is a rare sight - even though it doesn't mean "perfect", as some riders (and judges)
seem to believe. 10 means "excellent", and if you do see one awarded, it's likely to be
for an outstandingly good entry and halt.
9
Nine(9) is also a comparatively rare sight on a test. It indicates that you and your horse performed not just well, but extremely well indeed.
8
is - as I explained above - often the top mark awarded by a judge. An 8 on a movement would mean that your horse's engagement, energy level, outline and obedience were entirely appopriate for the level of competition, and that you demonstrated not just quality but also accuracy (making your transition precisely at the letter, for example).
7
is a good mark, and you'll need to be paying close attention to see just why a judge marks a 7 instead of an 8. If the movement were performed like the one that got the 8 score, with just a little bit less accuracy (making your transition just before or just after the letter, for example) or a brief moment in which the horse hurried or got above or behind the bit, the score of 8 would drop to 7.
6
means that your horse was obedient and performed the movement reasonably well, making the required transitions, performing the required gait, and going from letter to letter steadily, but there was nothing outstanding about the way it performed the movement.
5
means that your horse did what it was supposed to do, and was probably obedient, but may have been above the bit, on the forehand, or lacking in energy.
4
means that something was noticeably wrong with the way the movement was performed - the horse might have been bent the wrong way on a circle, very late or very early with a transition, or it might have thrown up its head and made a rough transition. Other possibilities might be a complete lack of energy - or an inverted silhouette, with a high head, dropped back, and trailing hindquarters.
3
means that there was serious trouble with a movement. For example: If the horse performed a late transition as above, but also showed marked resistance, the score would drop from 4 to 3. A very disobedient horse, a very resistant horse, and a very stiff horse will all tend to get a good many 3s.
2
If you got a 2 anywhere on a test, you're unlikely to forget the reason why - something must have happened! If you can remember a movement during which your horse bucked, reared, or shied dramatically across the arena, you have probably found the source of that 2.
1
Again, this is an unusual mark that you'll tend to remember. It means that something happened that was even worse than whatever got you the 2. ;-) If your horse bucked halfway around a circle, or shied across the diagonal, or did anything else that (a) showed great disobedience and (b) used up most of the movement, you might well find a 1 on your test.
0
This is the bottom - it means that the movement was never performed at all. This can mean a severe problem with the horse - or no problem at all. Even the worst, most unbalanced, resistant, counterbent, inverted, bucking horse can manage a 2 on a circle, or a 1 if it bucks repeatedly, but if it bucks and then charges off and never even gets to the point of performing any sort of a circle, or if it never halts at all, that would be a movement not performed. But there is another common cause of movements not being performed - a rider memory blip! If you simply FORGET to perform a circle, a transition, or whatever the indicated movement may be, you'll get a 0 for "movement not performed", but you shouldn't take the score as any indication of a comment on your riding or your horse's behaviour or training. Some judges will ring the bell for an error of course if a movement is left out - others will simply mark it "0" and keep going.