To calculate the number of spins needed for a sector of 6 numbers to win with a probability of 0.99 in European roulette, first determine the probability of not hitting any of those numbers in n spins. The probability of not hitting a number in one spin is 27/33, leading to the formula (27/33)^n = 0.01. Solving this equation will give the required number of spins. The discussion emphasizes understanding the calculations rather than just the results, indicating a need for clarity in mathematical expressions. This approach helps in grasping the underlying probability concepts in roulette.