Hmm I’m not too sure about that, but both scripts are made by the same person, so I think the difference is because the leech trainer script “will exclude any leech that is too recent (less than 24 hours since the last review), or too old (less than half the time between reviews remaining), or already trained” – so maybe the 50 you’re seeing with the dashboard script are considered “too new” or “too old” for the parameters of the leech training script?
I don’t know of any other script similar to it, the next best thing I can think of is the Self Study: Quiz Edition script, and you could just include the leech items you’re having problems with