Scales and weights were called balance in ancient times, It's a  balance of "balance advantages and disadvantages".

In ancient times, Half a Kilo was sixteen taels, and half a catty is eight tael, So we use six of one and half a dozen of the other to describe the equals.

Why is half a Kilo sixteen taels?
Why are there sixteen stars on the scale rod?

There is a saying that the Nandou has six stars and the Beidou has seven stars, Plus Fu Lu Shou three stars, a total of sixteen stars.

The Beidou seven starts are intended to warn people to have a direction in their minds when using scales, not to be greedy for money, and to distinguish right from wrong.
The Nandou six stars warn people to be centered and not skewed when using the scale.

If we are short in weight when we are doing business,

Missing one point, the less is Fu
Missing two points, the less is Fulu
Missing three points, the less is Fu Lu Shou