Hi Snehal!

The paper checking of CBSE is always done in a fair and unbaised form. The checkers are provided a model answer key where the distribution of marks is given there.

Step marks are also included in it and mostly they follow according to that key. There are times where 1 mark is awarded for writing given things wheras there are case where the enitre 5 marks is awarded for the diagram and labelling only. However there isn't any harm in writing extra .

hope this answers your query,

cheers!