Default [Q] Wierd Internal Memory Problem ?

I Am using Sony Xperia ZR ( Not Rooted & Unlocked ) . I Am getting wierd issue with internal problem that in phone settings Internal Memory Shows Free upto 713 MB but When I Connect Phone To Pc It Shows Only 345MBw . I Don't Know Whats The Exact Problem Is , Please Help Me With It .I Had Attached My Screenshots With Below
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Name:	In PC.jpg
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Name:	In Phone.jpg
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