Wherever a tool asks which pages to act on, the same rules apply:
5— a single page.2-6— an inclusive range.8-— page 8 to the end.-4— the start through page 4.1,3-5,9-— mix them freely.
Leaving the field blank means every page.
Order matters when organising
In the Organise tool the sequence is literal: 3,1,2 puts page 3 first. Repeating a number duplicates that page, so 1,1,2 gives you page 1 twice.