Optional; found on the Additional Data tab. For ASC 842/IFRS 16/GASB 87, the lessor's initial direct costs must be known to determine the implicit rate for the lease, which is defined as the rate that makes the present value of the rent plus unguaranteed residual equal to the fair value of the underlying asset plus the initial direct costs.
If this is shown as "Unknown," no implicit rate is calculated. If you know the amount of lessor IDC is zero, you should enter an explicit 0, rather than leave it blank.