I believe what they are referring to is 1:1 ratio in reference to the current ratio/price of Bitcoin compared to Litecoin. Meaning they are seeking to get the current price of Litecoin, without losing any value in the exchange.

I would be willing to do this exchange for you, but not at a 1:1 ratio, would you be willing to give me a 10% premium so that it is worth my time? I pay you for 4.05 LTC, you pay me 4.5 LTC. Let me know what you think.