Is it compulsory to work 9 hours?

In my current project I am working 8-8.5 hrs daily from office. But my lead and manager are saying that I am staying less than 9 hours so Upper management or HR may take action against me . They have shared me the shortfall hours for last four months (i.e how many hours short of 9 hours) . So generally I do 8 hours daily so for 22 days it is 22 hours short. Like that, they have shared for last 4 months.

What action they can take? Can they terminate me on this basis?

I am C1, 1.5 yrs experience.