It's arithmetical progression, but it works not like you are imagine it. All entries exists in the same database (it's about games, companies and who knows what else). And number is unique identifier - actually, _only_ matter identifier. Others are tags and placeholders that means nothing for database. So if someone would publish game #123, and next entries will be translations to Spanish and German, it would be #124 and #125. But if someone will publish another game after #124, it will be #125, and hypothetical German translation will became #126.
There is no internal connections between reviews (and it's another old headache of me), and all such connections mantained into some other databases. You totally can try "url hack" and call any review by it's number. Only remember that it will bypass all external connection, and replace it with given tags. So, for example, take your Spanish Dragon's Lair:
http://www.abandonia.com/es/games/27...%20Castle.html
es is the Spanish tag. "Games" indicates that it's from games database. Number is unique. Name means nothing at all.
So if you'll supply, say, finnish tag (fi) and give it any other name (Commando.html), but remain the number - you'll see the same page.
http://www.abandonia.com/fi/games/27262/Commando.html
Only system "thinks" it's Finnish now, and made all interface appropriate way.
So there are totally exists "lost" games in database if something was changed in the wrong order, game was never published or removed from publication. And you can accidentally find such "non-connected" reviews, if you'll set random numbers. (Actually, I did it when I downloaded all site content - unfortunately, I never sorted it out).