You simply referenced a body mass index (BMI) table and found the weight that placed you in the "green" 18.5-24.9 BMI range (BMI values of 25.0-29.9 represented "overweight" and values of 30.0+ represented "obesity"). Coined by the famous nutrition researcher, Dr. Ancel Keys, in the 1970's, the BMI was a ratio of a person's weight versus their height (technically weight (kilograms) / [height (meters) 2].
BMI can be a helpful tool due to how inexpensive and accessible it is. Aside from a scale, all you need to calculate your BMI is a calculator or online tool. However, while BMI is a quick way to determine your weight classification, it might not be the best choice for everyone.