The exam is national in name but the number of admission seats is distributed by region. A dense, competitive region needs a higher score to enter the same university than a smaller region does.
This is not a secret and it is not accidental. Universities administered by a city or region tend to enrol more students from that region, and the biggest universities are concentrated in a handful of areas.
The upshot is that your score is only meaningful compared to other students in your own region. National ranking lists exist but are not what universities actually use for admissions.
One consequence: relocating specifically for the exam is legally and practically difficult, and the authorities actively discourage it.