RussR
En-Route
Since being pedantic is a requirement on POA, I think it only has to be 50.00000000001 (or less) to be considered greater than 50.
I think the real answer is it has to meet whatever the DPE's definition of >50 NM is. Does he use Foreflight to measure? A plotter? A geodetic calculator? Back when we used paper, this occasionally created some issues, as one would measure with a plotter and one would measure with software, and get slightly different results. To add to the issue, the cartographers are allowed to move the airport symbols around slightly for various charting reasons like not covering something else up. I forget what the tolerance is, but it might have been like 1nm. That will throw off your measuring with a plotter!
I remember discussion where the airports were so close to 50 NM apart, people started arguing that measuring between airports was shorting them distance, and they should measure between runways, or takeoff and landing locations on the runway even.