What does the "Blobstore Stored Data" in the quota details of Google Appengine refer to exactly?

I am trying to understand what the "Blobstore Stored Data" refers to. My app has about 4 GB of uploaded images into the blobstore (not datastore). However when I look at my quota details in appengine, I notice that the quota being used up is the "Total Stored Data". I was expecting to see the "Blobstore Stored Data" being used up instead (which in 开发者_Go百科my case is still at 0%). Why is that the case?

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Blobstore Stored Data represents what you think it does: the amount of data stored in the blobstore. There are two types of quota in App Engine, though: billing quotas and limits. "Total Stored Data" is a billing quota; "Blobstore Stored Data" is a limit. Limits tend to be set very high, mostly to prevent runaway apps and abuse; if you run out of one of them, we'll generally extend them for you. Storage in blobstore is counted towards both quotas.

It's likely that you're seeing 0% on "Blobstore Stored Data" because the limit is set high enough that you're not even using 1% of it. What is the actual value of that limit, as opposed to the percentage value?