Returning tokens for the 10 token limit: which ones?
You may return any of the tokens currently in your possession.

When you collect gems and/or gold, you may collect fewer tokens than you are entitled to collect. It would be a little weird to collect tokens and immediately return them, but that addendum indicates it's perfectly valid to do so.

It doesn't mean you can only return those you've drawn.

It doesn't mean you can return more than would be necessary to avoid exceeding the limit.



The Splendor rules are quite poorly written. What follows is the complete rules (except the setup instructions) rewritten in much clearer language.

Rules of Splendor

[These rules are found here as text and as images suitable for printing on 3.5" x 2.5" cards.]

Setup:

 Players     Gems       Gold     Dev Cards   Nobles  
---------  ---------  ---------  ---------  ---------
    2      4 of each      5      4 of each      3    
    3      5 of each      5      4 of each      4    
    4      7 of each      5      4 of each      5    


On your turn, perform the following steps:


Take one of the following actions:


Collect up to three different gems.
Collect two gems of a type of which at least four gems are available.
Reserve a face-up or face-down development card and take up to one gold,
but only if you have fewer than three development cards currently reserved.
Reserved cards are kept private.
Purchase an available or previously-reserved development card.

Replace any missing development cards if possible.
Discard down to ten gems and/or gold.
Form a permanent alliance with an unallied noble whose requirements
you meet (if possible). Nobles are not replaced.
The game ends if any player has 15 or more points, and if all of the players
have had the same number of turns. Those with the fewest development cards
win ties.