FSRS + Review Heatmap: Systematic discrepancy between predicted and actual card counts

Anki Scheduling
1

Problem Description

I’m experiencing a consistent issue with FSRS and the Review Heatmap add-on where there’s always a discrepancy between the number of cards predicted for tomorrow versus the actual number that appears the next day.

Example: Yesterday, the heatmap showed 113 cards due for today, but when I started my session today, I actually had 132 cards to review (a difference of +19 cards).

This happens systematically - the actual count is always higher than what was predicted the evening before.

My Setup

  • Anki version: 27.07.5

  • FSRS: Enabled with default parameters (optimized)

  • Review Heatmap: Latest version

  • Easy Days: I initially had Easy Days configured for Saturdays, but the prediction discrepancy was occurring between Wednesday and Thursday, so I don’t think it’s related. I’ve currently removed Easy Days (just changing the setup in options of the deck but I’m not sure is was take in count.

  • Learning steps: 1m 10m

  • Desired retention: 90%

What I’ve already tried

  • Checked synchronization across all devices

  • Verified FSRS settings are consistent

  • Confirmed learning steps are under 1 day

Questions

  1. Is this discrepancy normal behavior with FSRS due to its dynamic recalculation?

  2. Are there specific settings that could minimize this prediction variance?

  3. Does the Review Heatmap add-on have known limitations with FSRS forecasting?

The discrepancy makes it difficult to plan daily study sessions effectively. Any insights or solutions would be greatly appreciated!

Additional Context

I suppose that’s maybe cause by my Easy Days configuration. Could these features be contributing to the prediction inaccuracy?

Thanks in advance for any help!

2

Does the built-in Future Due stats graph also show the same issue?

3

Yes absolutely, it’s very strange because just before clossing Anki (Monday after all my reviews) there is a number for tm (113 in the addon and in the stats) and the next day (Tuesday) there is a differents number (higher) in the addon and stats.

Thx for your help !

4

It has nothing to do with FSRS or with Heatmap. It most likely has to do with burying.

Scroll down the thread for more ideas about possible factors.

5

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