The NBA Over/Under Quiz works like the Over/Under bets in sports betting, except that here you do not bet on the future but have to answer questions about the NBA.
An Over/Under is given in this NBA Quiz and the user has to decide whether the correct answer is above (Over) or below (Under) that. Decimal places (.5) are used here because the answer is always above or below, but is never exactly the same as the Over/Under. For example, if the question is "How many titles has Bill Russell won as a player?" and the Over/Under is 9.5, the user has to decide whether the number of titles is above (minimum 10 titles) or below (maximum 9 titles). In this case, Bill Russell has won 11 titles, so the correct answer is "Over".
If the question is something like "How many points did Player X score in his career?", this means only the regular season (without playoffs) counts, unless otherwise specified in the question.