Bandwidth usage takes 24 hours to process for us, so you won't see that reflected on your dashboard until a day after it has taken place (this is for bandwidth usage only, and not for your play stats, which you can see just a few hours after they happen on your stats page)
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However, you can check in real-time how much BW is being downloaded per play, by using your developer console. Here are the steps:

Here's a screenshot of how that looks like:
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Happy monitoring!