In case that you are overriding the Initialize method of the provider the UncommitedFilesExpirationPeriod should be set explicitly, because in the base implementation of the method the property is set to 4 hours.
By "processed" we mean when the user postbacks the page and in the FileUploaded event the file is not set as invalid. This is applicable when the event is handled otherwise all files should be considered as "processed" after a postback.
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