Unable to understand 2 group flux

So i have a bare slab, im looking at the flux. i have energy filter and mesh filter. for mesh filter, my dimensions are 100,1,1 and for energy filter my groups are [0-1000eV, 1000eV-20MeV]. The first plot below is the two group, the second pic is single group flux. I don’t understand what it’s plotting against and why are are 200 date points as opposed to 100

WhatsApp Image 2023-11-20 at 12.19.29_4c366c1b
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