Just double checked mine. MY23 Plus Four.
The label show 50% Fill with a level line.
I read that as fill to the line with a 50% concentration coolant.
No mention of Min or Max
I have 18k+ miles so far and perhaps a thimblefull of top up with distilled water using my finger depth gauge with regular checks.
Only one leak found and that was a single drip from a jubilee clamped joint, fixed with a little tightening. All other joints checked and ok.
