ld is a unit of weight, pounds, and this is optional, so let's pick kg for both. ID means British pound, 1 pound (lb) = 0.45359237 kg (kg) electronic scale is based on the current and voltage changes to calculate the load weight, there are pressure sensitive chips under the electronic scale tray, people stand up, the resistance of the pressure sensitive chip will change with the weight, when the current is stable, the electronic scale will show the calculated weight of you. Because it is calculated by the program, it is normal to have some difference from the actual weight