Don't worry, you're not the first person to get confused by this.
I'm going to start completely from the beginning though, rather than try to answer the specific, because the chances of getting it wrong are pretty high.
EDIT: Ignore the wording about advanced skills. They're called Specialist skills now. They can't be rolled on unless you're trained. Otherwise, using an untrained skill is at a -20.
There are 2 types of skills in the game. Basic and advanced. Basic skills are things anyone can do (jumping). Advanced skills require training (say technical knowledge). In game, you can always make a basic skill check untrained, while you cannot make an advanced skill check untrained (more about training up next).
Alright, beyond that, a PC can have a skill in 2 major states: Trained and Untrained. If a skill is trained, you can make tests on it. If it is untrained, then you cannot test on it if it is an advanced skill or can make a test at -20 if it is basic.
Finally, there is something called skill expertise. All skills are trained initially in the +0 state. You can further advance it by +10 or +20 by spending more XP (see the advancement tables for cost).
So to specifically answer your question: If you are just trained in the skill, then it is +0. However its entirely possible that you have the +10 skill expertise.
It is possible that the test is easier, and is made at a +10 bonus by the sheer ease of the type of test. Often they describe the type of test too so say "Easy(+30)" or "Hellish(-60)"
Finally, a test can recieve a situational bonus. All these bonuses stack to a cap of +/- 60.
For others, I was never certain though if you add in skill expertise as a bonus to that +/- 60 cap.