A clean before-and-after observation is more useful than a dramatic number copied from a different account. Player progression, variants, boosts, updates, and collection size may all affect what appears on screen. This site therefore stores no universal rate in the calculator and asks you to supply the change that matches your session.
When the observed increase is greater than zero, a simple payback estimate divides the planned bid by that increase per minute. It answers a narrow budgeting question: how long would the entered extra income take to equal the bid? It does not prove that the target is fairly priced, that income remains constant, or that you will win the auction.
If the income units or timing are unclear, stop at reserve safety. You can still protect the cash you want to keep without making a payback claim. That degraded mode is intentionally useful because it avoids turning an uncertain observation into false precision.