Lets say you checked 5/5 french in your DCS, they will give you 4+4 points=8! BUT! Since you already know you will have an interview that means that you have passed 49 points for single/57 family, which is the good news, but you have to be very well prepared for the interview, because the immigration officer will test once again your french, he has the right to lower or increase your language points. I know it sounds crazy, but its absolutely true. I will tell you how they do this. They have a number of (ready) questions to ask you,related to your application, but as you know one question can be asked in many different ways, so this is what they will do, I guess they will start with something simple and keep going to see how much you understand them and how far you can express yourself. Thats why you have to be very confident on the interview and not get nervous or stressed, because this never helps. Also I believe that based on the way you express yourself you will get the points for adaptivity which are maximum 6 and you can get them only through the interview! I hope I dont sound too absurd, but this is my hypothesis!