It's more of a ranking list, of coins you would accept in trade for your coin. So if you only had one coin, but would trade any other coin in the whole Math Trade for it, your string would be 1000 coins long. Which is perfectly fine. Although, most people just put their top 5, or 10, or whatever. Me, I put about 100 choices for each coin, figuring I'd rather get a new coin than keep the one I have now.
TMA
Ok, another question, as this is the 1st year I've participated. Do I rank a general wish list? Or a ranked list of what I'd accept for each specific coin.