Aimpoint magnifier question

[Greywolf]

OK, I'm trying to figue out what the eye relief is for the Aimpoint 3x magnifier (going to use it with an EOtech sight).

So far I have found:

"at 5° FOV 40 – 90 mm at full FOV 60 – 65 mm"

WTH does this mean? Admittedly I am a noob, but what is 5 degrees of FOV vs. the Full FOV, and why such a huge spread on the eye relief?

I like maximum eye relief (used to 3.5"-4.0" from my Zeiss and Sightron scopes).

Thanks for the help!