The duration of IGNOU BSc practical depends on the credits of the particular course you have opted for.
For example, if your practical course is a 4 credit course, then you have to learn lab work in that particular course within a 13 days period.
Sign on the attendance sheet daily during this period
Maintain observation record of your practical work in your practical record book
At the end of the day evaluate your practical records with your professor.
On the 14th day, appear for the practical examination and viva.
Normally you get a minimum of 60% in the practical exam. You will lose these marks if you miss the practical exam.