The Rounded script returns only advance numbers that are in between the lowest number advance with 1% or higher odds and the highest advance number with 1% or higher odds and the rounded version rounds all numbers to 2 decimals.

The regular script returns not rounded odds for ALL possible advance numbers.

You can find what areas have how many NPCs and what each NPC type number between 1-21 means in this document https://docs.google.com/spreadsheets/d/1_t2IkxE8N7vet5HlfyBa8LP6oY8-J9URdy8hnSgJB08/edit?usp=sharing