How swimmingStrokeCount is counted? (both arms or one)

Hi! I'm making a workout app for swimmers. Our QA is confused with the swimmingStrokeCount output. He's a sportsmen and when crawl he used to count 2 strokes per cycle, one for each arm. The output is incorrect and looking at numbers we suspect that HKWorkout counts only one arm.

Documentation doesn't say anything about it.

How swimmingStrokeCount is counted? (both arms or one)
 
 
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