Same. Hard as I try I can't seem to get my ear tuned to hear the difference between plural and feminine and I generally have to depend on verb context, but that didn't help me out here. I should have listened to the slow version to ensure I was hearing what I thought I heard.
"dernier/dernière" can mean: last, latter, latest, final... It very much depends on context.
- last week : la semaine dernière
- I have a cat and a dog; the latter is black: j'ai un chat et un chien; ce dernier est noir
- he gave his final speech : il a donné son dernier discours (or: discours final)
Here it is latest, because it is about the more recent letters
Ordinal adjectives (premier, deuxième, ... dernier) generally go after notions of time, but sometimes they are placed first for a more subjective meaning:
la dernière semaine, il a beaucoup plu (subjective) = on the last week,...
la semaine dernière, il a beaucoup plu = last week,...
To know more about "fickle" adjectives (dual position vs noun): click here