Three, honestly unresolved at the time of writing.
Is thirty the right number? It was chosen because it is achievable by hand and small enough that failing is unambiguous. It might be too small to distinguish a real retention curve from thirty people being polite to a founder they have spoken to. What would settle it: whether the retained accounts include any who arrived with no human contact from us at all.
Does a directory listing produce users or just installs? A listing is discovery at the moment of need, which is the best kind, but it is also a one-click add with no commitment. Nobody we asked had a number for how those two compare. Settled by the first month of listing traffic against the write trail.
Is "capture weekly" even the right retention shape? Some genuinely valuable work is monthly. A weekly bar may be selecting for a usage pattern we invented rather than one that exists. What would settle it: the distribution of intervals among the accounts that do come back, rather than the count above a threshold we picked.