In horse trials low score wins. 30 would mean a dressage score of a 70 in dressage only testing. Depending on the judge scores vary greatly. Compare movement by movement and see where it varied. Posted via Mobile Device
I wouldn't get yourself too fussed over scores.
I ride Dressage, and find that if you focus soley on percentages, you will get disheartened. I'll get a score in the high 60's, come home and think right I've got this, this and this to fix. Do the same test a month later, feel like I absolutely nailed it and deserved at least a 70%, and end up in the low 60's.
Different judges reward different work. Particularly in the lower levels, its very subjective. Some judges like a horse that is up and happening with flashy paces, others like a horse that does a nice, quiet accurate test.
I am very lucky that my current horse is quite uncontroversial, so scores pretty well even with a test that felt poor to me. He is a rhythm machine, so even if I feel like he's ripping my arms out of their sockets, he looks like he's going around happily to the people watching!