For the pool swimming mode on the Xiaomi Watch/Xiaomi Smart Band, you need to set the lane length before starting. If the actual lane length does not match the set length, it can cause discrepancies in the recorded distance and number of laps.
The number of laps on the watch/band is recorded based on the number of turns detected. If you turn around before reaching the end of the lane or if your turning technique is not standard, it will cause the device to miscalculate, leading to inaccuracies in swimming distance and number of laps.
Please verify whether the firmware of the Xiaomi Watch/Xiaomi Smart Band is up to date.