Update README.md

README.md

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 license: cc0-1.0
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+# **IMPORTANT UPDATE (July 22, 2026):**
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+**We have updated the dataset to resolve a configuration issue in the simulations. To ensure a fair competition for all participants, we cannot currently elaborate on the specific nature of the issue or the fix. Any models that were fit to the previous dataset must be refit to this new data before submission. We sincerely apologize for any inconvenience this may cause.**
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+**The data for the beginner tier events (RMDC26_000001-RMDC26_000188) are not affected by this update, and are still valid for submission in the experienced tier of the challenge.**
+
+**Please also note the following technical details regarding this update:**
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+* **The saturation flag for some data has changed. We do not recommend using saturated data.**
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+* **We do not recommend using astrometric data if the photometric signal-to-noise ratio in that band is less than five (SNR < 5). Below this SNR threshold, the astrometric simulation produces unphysical values.**
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 # Experienced Tier
 
 The experienced tier data can be found in **RMDC26_Experienced_Tier_test.parquet**. If read in properly, it should have a shape of 103,281,456 rows × 18 columns and contain lightcurves for 2,087 unique events (event names range from `RMDC26_000189` to `RMDC26_002288`, with 13 events excluded). The columns are as follows.
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 ## Dataset Statistics
 
-- **Total rows**: 103,281,456
+- **Total rows**: 102,885,552
 - **Unique events**: 2,087
 - **Observations per event**: 49,488 (all events have the same number)
 - **Filters per event**: All events have observations in 3 filters (F087, F146, F213)