How daily reconciliation works
Reconciling is simply checking that what you sold equals what you collected. Add your M-Pesa received and the cash in the drawer after removing the float you started with. That total should match your recorded sales.
If it does not, the gap is information. Short means money you expected did not arrive, usually an unpaid credit sale, a payment to the wrong number, or cash taken out and not recorded. Over means a payment came in for a sale nobody rang up. Doing this daily keeps any gap small enough to trace.