To read scales, you need to know what each division represents.
To do this:-
This then gives the value of each division
Example

Example
What is the measurement at the level of the red dot ?

The difference is 500 ml and there are 4 sections.

So each pip is worth 125 ml.
The dot is 3/4 of 500ml.


Example
What is the measurement at the level of the red dot ?

To find each pip :

Red dot :

