What determines "grime" when it suggests recleaning?

My robot says more often than it should that there are areas with grime, even though the water is nearly clear that I pull out of the waste water tank?

Is it determining it based on the water?  Or other ai sensors?

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Hello ZA280993,
Hello! Thank you very much for your question. Here is the difference between Standard mode and Max mode. Use Standard mode for light dirt, Max mode for heavy dirt.
Standard saves more water, Max delivers deeper cleaning.
Standard Mode: Supports grime detection. After full‑house cleaning, it will re‑clean heavily‑soiled areas. Great for daily household maintenance, efficient and hassle‑free.
Max Mode: Supports grime detection. When dirt is detected, the mop will be washed one extra time. After finishing the current task, heavily‑soiled zones will be re‑cleaned specifically. It adopts denser bow‑shaped cleaning paths with slower speed, and focuses on high‑dirt spots such as dining‑table and chair areas. Suitable for thorough deep‑cleaning during big house‑cleaning. We recommend enabling resume‑from‑breakpoint before using this mode.
You may choose the proper cleaning mode according to the actual dirt condition in your home.
If you have any further questions during usage, feel free to contact us via private message. Wish you a pleasant experience!

Thank you! But what sensor is it using to determine what areas has grime?   Water or ai?