Quests in Dragon Quest XI get added to your Quest Catalogue as you advance through the Acts. The original quest list is just 26 quests but this will soon expand to 45 at Act II and then 60 by the end of Act III. As quests get added to the list, some will take the place of previous numbered quests. For example, Quest 17 is Light It Up in Act I but during Act II, becomes Quest 18 and a new quest becomes Quest 17.
For this reason, you'll find the quest numbering for this section begun in Act I and as such, the numbers will reflect when this walkthrough encountered them during the playthrough. Rest assured, all quests are covered and contain their title to make it easier to find the quest you're looking for.