Mixing water with MOTUL Moto-Cool coolant

So I picked up 2L of motocool from RC, John mentioned that I might only need to mix it with a tiny bit of distilled water to top of the reso, but looking at the manual, the capacity is closer to 2.65L which means that I'll have to mix an extra .65L of distilled water, which is quite a bit more..

This is for my K7-600 street bike that I'm converting back for the street so need to keep coolant in there for the winter/next year, will the extra .65 of water **** things up and freeze or should it not be a problem mixed in? Or should I just go back and buy another bottle?

Thanks!

The motul coolant is premixed I would get another bottle cheap insurance to not have the coolant freeze in the winter and trash the motor.

If the original stuff was mixed 50%, your new blend will be near 37% glycol. Minor research indicates that the freezing point of that blend is near -23 C. If the bike is staying in a place somewhat protected from outside temperature (e.g. a garage which is unheated, but attached to a house) it will probably be okay (my garage never gets anywhere near that cold) but if it is in a shed, or is otherwise pretty much at outside-air temperature, I wouldn't risk it.