I got that figure from memory and tried to verify it, But Zimparks hasn't updated their website since 2017.
Zim. is actually 9.2mm, i would guess to allow the old 360 nitro cartridge.
there are other countries with no requirements at all if I remember correctly. Mozambique, Ethiopia, Benin and a couple others.
Another case of a writer having to produce 2500 words to get paid.