The "den" suffix adds the meaning of "from" to the word. So, "öğleden" would mean: " from noon".
For example: * evden [two parts: ev-den] means: "from the house".
Remember also that suffix "de" means "in", so for example: * evde [two parts: ev-de] means: "in the house".
I think this is the noun. I mean in English, you wouldn't just say "Afternoon" because it wouldn't make sense alone. However, in other languages like Arabic and it seems also in Turkish, if someone asked you about a time, you could simply say " Afternoon" and it would mean :"In the Afternoon". I think this is why in the translation above, they made sense of the word by adding " In the ...".
Sometimes mistakes are due to missing word "the" which does not sound correct because we are learning turkish and not English. Moreover word the is not that important as the sentence makes sense with or without the. Please make some correction as due to this we loose our life line, Hearts i mean.