26 Adar (Pesach)

On Pesachim 108a there is an argument which two cups Rav Nachman holds you have to lean by, the first two or the last two. If it's the first two the reason would be because that's when the freedom is happening. However by the last two, what happened, happened. What does that mean? You should for sure have to lean by the last two cups because then you're actually free? But even more, why on earth would you lean by the first cup? You're not free!