Problem with the Apple HealthKit to obtain accurate sleep data

Question

I am developing an application that tracks users' sleep habits using HealthKit's sleep monitoring function on iOS. However, I am experiencing a problem with the accuracy of the data returned by the function.

I checked that the code for retrieving the data is correctly implemented and there are no obvious logical errors. I have also checked that the data is available in the device's Health app and it appears to be recorded correctly. I took a good look at the Aapple documentation and asleep is now deprecated

I was wondering if anyone could suggest potential causes for this problem and provide guidance on how I can get more accurate sleep data using HealthKit. Could there be some setting or configuration I'm overlooking?

    func fetchSleepData(completion: @escaping (String) -> Void) {
        guard let sleepType = HKObjectType.categoryType(forIdentifier: .sleepAnalysis) else {
            completion("0 hours 0m")
            return
        }
        
        let sortDescriptor = NSSortDescriptor(key: HKSampleSortIdentifierEndDate, ascending: false)
        let query = HKSampleQuery(sampleType: sleepType, predicate: nil, limit: 1, sortDescriptors: [sortDescriptor]) { (query, samples, error) in
            if let error = error {
                print("Error fetching sleep data: \(error.localizedDescription)")
                completion("Error")
                return
            }
            
            guard let samples = samples as? [HKCategorySample], let sample = samples.first else {
                completion("No sleep data")
                return
            }
            
            let duration = sample.endDate.timeIntervalSince(sample.startDate)
            let hours = Int(duration) / 3600
            let minutes = Int(duration) / 60 % 60
            let formattedSleepDuration = "\(hours) hours \(minutes)m"
            
            completion(formattedSleepDuration)
        }
        
        healthStore.execute(query)
    }

I have implemented code to retrieve sleep data using HealthKit, but I have noticed that the data obtained does not seem to be accurate. For example, the number of hours of sleep recorded seems to be less or more than I would expect, and there are significant discrepancies between the data obtained and the user's expectations.