As usual, it’s probably because of SDM RENDAH.
As reported by the infamous Kominfo’s article Indonesia was placed at 60 of 61 country in 2016 cited from World Literacy: How Countries Rank and Why It Matters (Miller & McKenna, 2016).
Current rank UNESCO 100 of 207, more comprehensive report by OECD’s Programme for International Student Assessment (PISA) 2022.