Quick Coolant Flush mixture question

[Markt213]

This is my first time flushing my 05 987 S. Based on everything I have read I will not get all the old coolant out. Possibly only 4 or 5 of the 6 gallons. I will flush with distilled water which will mix with the remaining coolant then drain that out leaving over a gallon of diluted coolant in the car before I put my new 50/50 in.

My question is do I need to worry about the overall mix in the car being less than 50/50 because of the remaining coolant? Should I mix my new coolant possibly 60/40?
I could be over thinking this but I don’t want to screw it up.

Thanks for the any help!