It is true that most word bank exercises contain exactly four extra words. (This has helped me more than once when I had five words left over.) Some have no extra words at all but I don't remember seeing one, two, three, or five.
This applies to the browser version; in the mobile app, fewer than four extra words seem to be not uncommon.
@Qurraguina - yes, that's how we learn them at primary school. Children begin learning this by memorizing "První pád: kdo co. Druhý pád: koho čeho. Třetí pád: komu čemu. Čtvrtý pád: koho co. Pátým pádem oslovujeme, voláme. Šestý pád: (o) kom čem. Sedmý pád: kým čím".
All Czechs know cases by numbers, only few know the Latin names (nominative...) But when teaching Czech, the Latin names are used exclusively, just like they are used in linguistics in all languages.
You should start submitting button reports. There are only two recognized translations, and the only difference between them is the pronoun. And because the system often reacts to any error by showing the main translation, it can create the wrong impression that the problem was the pronoun.