Things I don't understand about GFXBench results!

[imacken]

If I look at the results of a test, say Manhattan, in GFXBench Metal for my M395X 4Gb, a few things puzzle me.
1) my 3128 frames is way down the list looking at the Compare with other devices tab, to the extent that it is below 21.5" late 2012 iMac (3305) and others which I would not expect.
2) if I look at the ratings here the same card appears pretty high up the list. Is this a different spec to the iMac 5k version?
I'm confused!

 

[Samuelsan2001]

Benchmarks are complicated and an indication at best, mainly the software and firmware can effect things way out of proportion to the hardware capabilities making every card and make of card perform differently on different benchmarks when in different machines using different OSes. In other words one benchmark result in isolation means practically nothing.