Update README.md

README.md

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     └── low_parquet/
 ```
 
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 ### Directory overview
 
 - `raw/json/`: raw trajectory and step-level structured records.
 - `raw/img/`: viewport-level images or cropped visual observations used for step grounding.
 - `raw/full_screenshots/`: partial full-page screenshots aligned with step context where available. This folder is not exhaustive and does not provide full coverage for all trajectories or steps.
-- `processed/high_parquet/`: higher-fidelity processed Parquet release for analysis, model training, and large-scale loading.
-- `processed/low_parquet/`: lighter-weight processed Parquet release for faster experimentation and lower storage / I/O cost.
+- `processed/high_parquet/`: processed Parquet files for high-level tasks. Each sample typically includes the user instruction, action history, and the current page screenshot, and is mainly used to evaluate or train planning ability.
+- `processed/low_parquet/`: processed Parquet files for low-level step prediction. Each sample typically focuses on the instruction for the current step (for example, “click xx”) together with the current observation, and is mainly used to evaluate or train grounding ability.
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 ## Dataset summary