I avoid buying eggs from southern hot states. Two two separate orders of red jungle fowl eggs from Texas and Florida both ended up cooked dead. Unfortunately red jungle fowl are more commonly kept in warmer climates.I usually speak to fertility (things that progressed at all vs clears), and viable hatch rate vs total hatch rate.
So if 15 of 20 eggs are fertile/progress, that's a fertility rate of 75%, but 5 of those eggs quit or are DIS at hatch, that's a viable hatch rate of 67%. The total hatch rate would 50%.
Sometimes I even break it down further into the post-lockdown hatch rate, so I can see where things were just quitters versus where I had issues with hatching.
As a person who uses shipped eggs, I find this to be helpful, because it lets me figure out:
1) How many eggs I actually need to order based on my past experience;
2) Which sellers (or shipping routes) don't do well for me; and
3) Where the problems are with my technique/equipment.
All that to say . . . unless people are being specific, I don't think you can assume what a hatch rate means, but I concur with hysop that two numbers don't give you the whole picture.