In Financial Terms, How Does a ‘Share’ Represent a Miner’s Fractional Claim on the Expected Block Reward?

A share is a unit of work that serves as a probabilistic measure of a miner's contribution to the pool's collective effort. In financial terms, each valid share submitted grants the miner a fractional claim on the expected value of the next block reward.

The total reward is divided among miners based on the proportion of shares they contributed to the total shares submitted in the reward period.