The issue I've encountered with my recent attempts at character creation are that, we'll I don't really understand where some of the numbers come from, the rules say do it 1 way and on character Stat block in the book you get something like +12 (2d8 +17) in this case 2d8 is a lightsaber. My question is where do the other numbers come from and how are they calculated?
In the stat-blocks, the attack damage includes the base damage, and any bonus damage stemming from heroic levels, ability score modifiers, feats, weapon properties, etc.
For example, a 20th level Jedi, with an 18 strength wielding a lightsaber two-handed and no feats or other sources of extra damage, would deal: 2d8 + 10 (1/2 level) + 4 (str) damage + 2 (1/2 str) = 2d8 + 16 damage.
I just noticed a clarification comment on the question, so I'm adding a bit of information to this answer to help.
Assuming the attack is listed as: "+12 (2d8 +17)" The part inside the parenthesis is what was discussed above (weapon damage + all applicable sources of extra damage). The part before the parenthesis is the attack modifier associated with the attack.
So, in the "+12 (2d8 +17)" example, the attacker has a +12 modifier on their attack roll, and deals 2d8+17 damage.