Does it matter? You draw a line on the chart, if whatever it is is beyond that line it has to sail within that line if it needs a helicopter. Twenty or thirty miles isn't going to make a lot of difference.
Not quite so. Radius of Action varies with wind intensity, and it can be a lot. If wind is below 30 kts, in the Merlin, we're OK, but above that, range starts reducing, and if you have the misfortune of going out with a +45kts headwind, range reduction may be 15-20% (50-70 NM). So, the "line" moves a lot, and 20 miles make a lot of difference if you're going above 250/300 NM. You really need to get as much out of the aircraft as possible, but in the end the wind pretty much determines how far you can go...
Best wishes