The iHealth Edge tracker records all your activity (physical activity, exercise and sleep) from 0h to 24h. It is reset each day at midnight (number of steps, distance, calories burned, activity level). Unsynchronized data before midnight are obviously not lost, they remain in memory until the next sync.
For faster synchronization, a daily synchronization is recommended. But your iHealth Edge tracker can record up to 14 days of data.
If you have not synchronized your iHealth Edge within the 14 days, the oldest data in memory will be overwritten by new data.