what is the formula for calculating least count of an ammeter

plz give a example and diagram

Least count of a measuring instrument is the least value of physical quantity that can be measured accurately using the instrument.

It is represented as (total range of instrument / number of divisions on smallest scale)

For example, Take a simple scale (length measuring instrument) of 15 cm. In this scale, you can see that the 1 cm is divided into 10 equal parts. Therefore, the least value it can measure is 1cm/10=0.1cm or 1mm which is least count of this instrument.