why 4 entries for accelerometer log?

If I print out the entries from reading the log in the accelerometer, there are 4 entries:

2016-04-04 20:00:58.044 Simple MetaWear Test[809:301549] 0.004517,-0.003784,-0.002930,0.003799

Why are there not three entries?

[[device.accelerometer.dataReadyEvent downloadLogAndStopLoggingAsync:YES progressHandler:^(float number) {
                    // Update progress bar, as this can take upwards of one minute to download a full log
                }] success:^(NSArray<MBLNumericData *> * _Nonnull result) {
                    // array contains all the log entries
                    for (MBLNumericData *entry in result) {


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