Just a crazy, random thought. This may not be your problem at all, but it did confuse me a bit when I was first learning this stuff.
If you are working from the videoplayer example, and you are setting the Length attribute in showFeed.brs, it might be getting overwritten in appDetailScreen.brs. There is a line in appDetailScreen.brs (line 98 of the unmodified example code) that overwrites the Length attribute with the contents of the Runtime attribute. So, if the Runtime attribute is empty, that might explain your Length attribute not showing up.
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