How many rabbits are born at one time?

As low as one and up to 25. Small breeds the average is about 3-8 for medium to large breeds about 5-15. But anything 20 or over is extremely rare.
Well, there is no exact number usually small breeds 1-4 but if you have small breed a little bigger than normal maybe 1-7 ex. Mini Rex, Netherland dwarfs . The large and giant breeds it could be 6-16. I know that for a fact because my Flemish giant mix had 15 but if you have a litter on the larger side they might not a survive.