Fine cognac is often written on a label, but it does not say anything other than it is a good cognac. It has no official meaning and is not a guarantee for good quality.
If ‘fine’ is used in combination with a Cru indication on the other hand, it has a very specific meaning, that is, the cognac is guaranteed to be made 100% from grapes of that cru; for example: fine petite champage.
Fine champagne cognac – not the cru-name ‘grande champagne’ is used – is yet another designation. it is a guarantee that the cognac is made for at least 50% out of grande champagne and the rest of petite champagne.