Regardless of how many bedrooms are occupied as part of their tenancy agreement. You should always put the total number of bedrooms in the property your client is occupying when completing a Tenants Contents insurance application.
For example, if your client rents 1 room in a 3 bed house, 3 bedrooms must be selected.
This is because whilst your client might be in a shared house renting only 1 room according to the tenancy agreement, it doesn't take into account the property has 3 bedrooms with communal areas and other tenants who could have access to their belongings at any given time.
Your clients items are covered in the home i.e. the insured address including communal areas, not just their bedroom.
For full details on whats covered and whats not covered, refer to the policy terms and conditions booklet.