Unless you were using a certified scale and checking it with certified check weights every time you used it, you were just guessing and hoping your dealer wasn’t randomly or purposely off. And density of the material weighed matters also. Weed is far less dense than pasta so a discrepancy can be more noticeable since it takes a larger volume of weed to reach a particular weight than pasta does.
Understand that a digital kitchen scale is made with the cheapest load sensors a manufacturer is willing to pay for. Nor do they come with any kind of traceable certification as to accuracy class. In fact you get no guarantee that your shiny new kitchen scale is fit for even that purpose - just that it turns on, lights up, and displays something when you place a load upon it.
Accuracy is a cruel and VERY expensive mistress to chase. And most people don’t understand it anyway.