The boyz box actually comes in 10's.
the large box you have contains 2 box's of them, meaning that you will get 2 nobz.
Just some quick advice and rulings to help you by -
Nobz - These are restricted to 1 per boyz mob.
Each mob is 10 - 30 boyz.
So with those 20 boyz you can either take 2 units of 10 (each unit led by a nob) or have a single unit of 20 (with a single nob)
With orks they tend to do better in large mobs of 20-30
Special weapons - You should have a choice between big shootas and rokkit launchas in each box.
With the boyz you can take 1 special weapon (
BS or rokkit) for each 10 boyz in that mob.
So if you do 2 units of 10 you can take a single special weapon in each, and for 1 unit of 20 you can take 2 special weapons.
Nob layout - You should have a pole for him which goes on his back, this is worth taking
Other than that, give him a power klaw and a basic slugga for most effect.
Boyz layout - You can arm them with either sluggas + choppas or shootas.
If your going for shootas then i would take big shootas as a special weapon and use them as a shooty mob.
If you take sluggas + choppas i wouldnt waste time with special weapons, they get more use from thier basic weapons in the long run.
Hope that helps, and feel free to
PM me if you need any more help