I guess the he is saying once the fluorine make two bonds with the other atoms, then there is a plus charge on the fluorine, but this is highly unlikely. Fluorine is highly electronegative by itself, a positive charge on fluorine is highly unstable
for this molecule, O=-1 and f=+1, N=+1, the overall charge of the molecule is +1, the charge separation in this case is stabilized by resonance, or conjugation (some people would like to use this term to describe the effect more precisely)