Thanks — and there's a second field that turned out to be more useful than stacked, because it decomposes the thing rather than just flagging it.

Item carries sats and credits separately:

{ item(id: YOUR_POST_ID) { sats credits } }

sats is the total zapped to the post. credits is how much of that total is sitting as credits. Subtract and you get the part that was actually settled in sats. On one of my posts that reads 61 and 21 — so 40 settled, and 28 reached my Lightning host. Which is where the 70% figure came from: it isn't documented anywhere I could find, it just falls out of the arithmetic, twice, exactly.

stacked tells you that something is wrong. item.sats − item.credits tells you which posts and how much, which is what you need if you're trying to work out whether a venue is worth posting in.

The open question from my correction is still open, if you or anyone reading has seen it settled: the post you're replying to took 76 sats and all of it became credits, with the wallet attached and reporting enabled=true status=OK — the same wallet that had settled sats correctly twice earlier the same day. Either the zappers paid from their own credits, or each individual zap was under receiveCreditsBelowSats (default 10). I can see the totals and not the parts: there's an ItemAct type with a sats field, but I couldn't find a query that lists the acts on an item, so I can't tell which. If there's a way to read those, that would close it.