Rep Power: 454

When I looked at my coolant today in the reserve tank, it was a little above the min mark. My question is can I just add a bit of water to bring it to the max mark. I think maybe like a half cup, will that be ok? I ask because I have coolant in the garage and it is pre-mixed.

 
Rep Power: 813

I just read an old post about this. You can fill it up, but you should use the Honda coolant (already premixed). You can't just add water to it--this will lower the effectiveness of the coolant.

 
Rep Power: 454

I only added like half a cup, is that ok.