Where did the better-than-quoted output go?

Positive slippage means execution improved relative to the accepted quote on matching terms. To verify it for a fixed-input swap, compare the final received quantity with the accepted quoted quantity, then account for any separate distribution or charge rules.

Start with tokens received

Suppose an accepted hypothetical quote estimates 400 output tokens and the recipient actually receives 402. With identical input and fee treatment, the improvement is two tokens, or 0.50% of the quoted output.

If the wallet's dollar estimate rises while the token quantity remains 400, that alone is not positive slippage. The valuation price may have changed. Quantity and valuation are different observations.

Follow where the improvement settled

Do not assume that a larger amount observed somewhere in a transaction is necessarily the amount received by the user. The route can include intermediate transfers, fees or other recipients. Reconcile the final recipient's net balance change with the transaction's actual settlement terms.

The ERC-20 standard provides token balances and transfer events. Those are useful accounting evidence, although transaction interpretation must still distinguish incoming transfers from unrelated movements and identify the correct token contract.

A better fill can still have a higher total cost

Imagine the two additional output tokens are worth $0.10 each, while a changed transaction adds $0.40 of separate network cost. The token execution improved by $0.20, but net value is $0.20 worse than the original all-in estimate under those assumptions.

Report both facts rather than letting “positive slippage” imply an overall saving. When the original quote is missing, a favorable price comparison against a chart is insufficient to prove quote-to-fill improvement. Preserve the quote and receipt together, including whether quoted output was gross or after deductions. There is no universal rule that every execution service distributes every improvement in the same way.