The rent is calculated based on the number of bedrooms in the apartment, and not the actual number of people who live there. Your landlord must calculate your rent assuming that 1.5 occupants live in each bedroom (or one occupant, in the case of a studio).
So, the rent for a two-bedroom apartment, for example, would be based on three occupants (1.5 x 2 bedrooms) in the apartment.
The tax credit rent also includes a utility allowance.
The maximum rent you can be required to pay for a low-income unit in a tax credit property is 30 percent of a percentage (usually 50 or 60 percent) of area median gross income (AMGI).