Okay, this is special. A three-disk raidz with 14TB disks with 42TB of space? Maybe because it's a bhyve vm backed by sparse zvols? I mean... this isn't a thing, right?

zpool list -v db
NAME SIZE ALLOC FREE CKPOINT EXPANDSZ FRAG CAP DEDUP HEALTH ALTROOT
db 42.0T 3.19M 42.0T - - 0% 0% 1.00x ONLINE -
raidz1-0 42.0T 3.19M 42.0T - - 0% 0.00% - ONLINE -
gpt/s0d0-WD-08NRX3 14.0T - - - - - - - ONLINE -
gpt/s0d1-NCC-1701D 14.0T - - - - - - - ONLINE -
gpt/s0d2-TOSH-9268 14.0T - - - - - - - ONLINE -