tiny sensors got tiny lenses cause their focal lenght is around 16mm when tele and 3mm when wide angle .Why? The sensor size is a big part of a lens size. You can have wide apertures with very small lenses on cameras because the sensor is so tiny.
8mm wide lense with 16mm focal lenght is F2
but yeah looks like its more likely lens what size of field is equivalent with 100-400m full frame.