What it says on the tin; compare to overall wikipedia pageviews.
Answer: the vast, vast majority of requests are "unidentifiable" from a user agent parser POV; what that actually means is that they're all from Dalvik-based Android devices. Example user agent:
"Dalvik/1.6.0 (Linux; U; Android 4.0.3; A200 Build/IML74K"
This sort of thing is responsible for ~3.4m of 5m requests; the remainder are, in order, from Firefox v3, chrome v42, and further (identifiable) Android platforms.
(CC @Deskana )