Nikon Z 8 Reference Manual page 172

The number of shots determines the bracketing sequence:
No. of shots
2
3
4
[H1]
5
[H2]
If you selected 5 shots, you can choose from bracketing sequences [H1] and [H2] by holding
the BKT button and rotating the sub-command dial.
If you chose more than two shots, proceed to Step 3.
Off → Value selected in Step 2
Off → Low → Normal
Off → Low → Normal → High
Off → Low → Normal → High → Extra high 1
Low → Normal → High → Extra high 1 → Extra high 2
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Bracketing sequence
Bracketing