Kop & voettekst

Sounds like it ought to be neat, but the voice sounds MuseScore has are the pits. I literally cannot hear the sixteenth notes at all, at all.

The OP's question relates to Kop & voettekst (= Header & footer). It's the footer which is relevant here:

The footer includes a "Page n of 4" which is hard coded as:
Halaman $P dari 4

But using the $n shortcut for "Total number of pages", MuseScore will recalculate the page count to 5 pages even when the final measure overflows to a new page. So the footer should contain:
Halaman $P dari $n

[EDIT]
Use the menu path Format > Page settings ... > Scaling > Staff space to reduce the Staff space slightly. This will prevent an overflow (5 pages) and get back to the desired format (4 pages).