Each segment is one halving epoch (210,000 blocks / ~4 years). Bitcoin's block reward halves each epoch. All 32 epochs exhaust the 21 million BTC supply.
Middle Ring — Difficulty Adjustments in Epoch
Each epoch contains ~104 difficulty adjustments (every 2,016 blocks / ~14 days). This ring shows which adjustment you're currently in within the epoch.
Inner Ring — Blocks in Adjustment
Shows progress through the current 2,016-block difficulty adjustment period. Resets every ~14 days.