It's the trade deficit masquerading as a tarrif - Moldova sells more than it buys from America because American stuff is expensive and Moldova can't afford to buy American goods so it gets hit with "reciprocal" tariffs on it's exports.
I read somewhere that the theory is countries that don't purchase ad much from the us as the us buys from said country got more tarrifs because in trumps mind they're losing money.
Reporters could recreate the entire list exactly by asking ChatGPT/Grok/Claude/Gemini what would be an easy way to tariff other nations.
The tariff % is simply the US trade deficit with that country divided by imports from it.