The longer version
Reconciliation answers one question: does the money add up? The club takes the bookings, class spots, and membership charges for a period, the refunds against them, and checks the total against the payouts that reached the bank. Differences are explained or chased.
Clubs care because the gaps are where money leaks: a refund issued twice, a desk booking never charged, a payout that never arrived. Monthly is the usual rhythm for a small club, weekly for one with several sites or a lot of desk cash.
The mistake is reconciling against the bank statement alone. A payout is a batch, so one bank line covers dozens of bookings. Work from the payment list in the booking system to the payout list in Stripe, then to the bank, and keep the export from each month.