I think that the words listed may just show a random form out of the forms added in the lesson. (I'm not sure, maybe it showed 'dwanaście' as well). And as these are forms of one word, you won't necessarily get all the sentences that were created for this word, just some of them. There is a sentence "Pracuję z dwunastoma pracownikami", which shows that it is the Instrumental form of "dwanaście", i.e. twelve.
Thanks for that. It's very strange, but I have now been through the whole section on 'numbers' and the sentence you mentioned does not come up at all! I'm using the WEB version, so could it be only on the app, or something? It did give 'dwanaście' in the exercise and I realised 'dwunastoma' was something to do with 12 but I just couldn't get it! A lingot coming!
Well, I don't know how exactly it works, but I think if you take a lesson, you should usually get two sentences with each word. And there should be at least 3 sentences created for every word. So without strengthening, you just won't see some of them. And there also is the thing with the algorithm, at least in the beginning it may give you the sentences that are easier (less people struggle with them)... But really, I don't know much :)