Hi there! The characters must be 70mm, 50mm wide, and 10mm broad. The space between adjoining characters must be 10mm. Any space between letters and numbers must be 20mm. The margin between the nearest part of any character, and the top or bottom of the licence plate must be 10mm. The margin between the nearest part of any character, and the sides of the licence plate must be 20mm.
To get a better look at the measurements, you can refer to the image on this article: https://www.motorist.sg/article/203/5-fun-facts-about-your-car-licence-plate