Two-weapon fighting clarification needed

From the "How to Play" .pdf:

Two-­‐Weapon Fighting:
When you wield two melee weapons at the same time, you can attack with both of them using a single action, provided at least one of them is a light weapon. You take a −2 penalty to both attack rolls, and you use only the light weapon’s damage dice to determine its damage; you add no bonuses to it. If both weapons are light, only one of them is limited in this way (you choose).

If both weapons are light, only one of them is limited in what way? Do you deal damage with both light weapons? Does the light weapon you choose to deal damage with keep its bonuses? Does only one light weapon take a -2 penalty to attack rolls? 
Only one of the weapons doesn't get the modifiers. Meaning if you have two light weapons, they don't both lose their damage modifiers when attacking twice.
To be more concise:

You attack with two light weapons. Both attacks are at a -2. The mainhand weapon deals [W]+Str/Dex and the offhand (your choice if they're both light) deals [W] damage (with no Str/Dex).
Thank you, sir. Most concise.