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# Equality Boundary Settlement Precision Risk

#### Description

In ultra-short-term crypto prediction markets, if the settlement price is calculated based on higher precision (additional decimal places) than the value displayed in the UI, a discrepancy may occur between the price perceived by the user and the actual settlement price.

In particular, while only rounded prices are displayed in the UI, actual settlements may differ if full decimal precision of Oracle data is used, even if users perceive them as the same price.

In this case, even if market participants correctly understand the rulebook, it becomes difficult to predict the actual settlement results, and market reliability and predictability may be reduced.

#### Real World Case

{% stepper %}
{% step %}
In Polymarket's Solana 15-minute Up/Down market, there were instances where the market result was settled as Down even though the start and end prices were displayed identically in the UI.
{% endstep %}

{% step %}
The market rulebook defined that if the closing price is greater than or equal to the starting price, the settlement is to be Up.
{% endstep %}

{% step %}
However, the actual settlement was performed based on the full decimal precision of the Chainlink SOL/USD data stream, and the closing price was calculated to be slightly lower than the starting price due to additional decimal value differences not displayed in the UI.
{% endstep %}

{% step %}
As a result, although it was expected to end as 'Up' based on the UI price, a discrepancy occurred where it was processed as 'Down' during the actual settlement.
{% endstep %}
{% endstepper %}

#### Mitigation

* **Sort Display Precision = Settlement Precision.**
  * Match between user perception and actual settlement results
  * Eliminating hidden precision-based result discrepancies
* **Specify Settlement Rounding Rule**
  * Apply explicit rounding rules before settlement comparison
* **Precision Disclosure**
  * The UI displays the actual comparison precision.


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