That's another FAQ, definitely.
The first is the 8*8=64 TB your devices bring into the game.
You have configured a RaidZ2, so two of those are used for redundancy. This leaves 8*6=48 TB, theoretically.
From 48 down to 45.37 is not really far...
Just wondering if I'm missing something or is the pool size difference just a overhead thing.
Node>Disks>ZFS
shows I have 64tb
Node>Pool>Summery
shows I have 45.37tb