Q16 is a triode region transitor, i.e. a resistor, implementing a resistor. This allows tracking of the Q7's gm.
Q6&7 do amplify the signal.
They're assuming a unit transistor of W/L ratio, but they're not saying what's this base ratio. All we know is that they are scaled by those numbers, e.g 300*W/L. Apparently they're also using the same length, but this doesn't necessarily mean they're using the minimum length available in the technology.