Well I certainly hate their "tech page" gives unhelpful units...
If I read it correctly, that is a FFP, Mil/mil scope(the one you bought). But 50min total adjustment from a 34mm tube is wretched. That is about 15 mill total. My Primary Arms scope is a 30mm main, and has 34 mil total adjustment. The ERS is a SFP, so your adjustments don't match, worse offense in my book.
I can't speak to the glass. The SWFA 5-20 has about the same adjustment as my PA, and has better coatings.
Cheers
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