Translation:I bought envelopes and stamps in the shop.
Not sure if I can tell the difference between -ch and -gh. The way she pronounces clúdaigh sounds OK to me.
In an earlier lesson, with I believe the same speaker, there was something like "She is not thin s/he is not fat. She is perfect." Or something like that. (I tried searching for it in discussions so I could leave a link, but couldn't find it. Sorry.) I, and at least one other person, thought that she had spoken the lesson properly saying in Irish "she is not fat" and that the person typing the translation in English had miss-typed it "he is not fat." Whether miss-spoken or miss-typed, both the English and Irish sentences are grammatically correct and make sense but have different meanings. Is clúdach just a mispronunciation (which I presume most people would probably understand in any case and I'm guessing that this is the case)? Or does it change the meaning of the sentence?
clúdach litreach is the singular "an envelope".
The exercise that you are referring to is Níl sí tanaí ach níl sé ramhar. Tá sí foirfe. There is absolutely no doubt about the fact that the written lessons were created before the audio recordings - the speaker misread her script, it is not a transcription error. The current recordings were created at least two years after Irish course was released. The current audio recordings were released in April 2016. The first comment on the English to Irish exercise "She is not thin but he is not fat. She is perfect." is dated 11 months earlier, in May 2015.