V7 of F Major is C7, so it's saying that the II7 chord is leading to the dominant 7th, which then resolves to the tonic? I think? 
Yeah, that's pretty much it.
We are in Bb major, which has this scale: Bb C D Eb F G A Bb.
So based on diatonic harmony, the ii chord should have C Eb G (maybe Bb)... C minor. It would be perfectly fine and very common to have Cm going to F7 going to Bb, ii - V - I. All over classical music. All over pop music.
But instead of Cm we have C7, that is C E G Bb. So where is this E natural coming from? Well it is borrowed from the key of F major. F major has F G A Bb C D E F. Based on diatonic harmony, the V7 of F is C E G Bb, which is our chord.
So what does F have to do with anything? Well F is the V of Bb. So we have C7, which is the V7 of F, leading to F7, which is the V7 of Bb, leading to Bb, which is the actual tonic. That makes C7 the "V of V", because it is the V of F which is the V of Bb. Or at least that is the classical way of explaining that chord.