The raw value of a debt estimation is based on a time-span.
An object of type IDebtFormatter can be used to fomat the debt estimation into man-days, man-months, money or ratio or rate.
In CQLinq code rule, debt values are obtained by casting explicitly a System.TimeSpan value to a Debt value, or by naming a TimeSpan column Debt (in which case TimeSpan values are automatically converted to Debt values.
Also such debt value obtained in a CQLinq rule context is multipied by the DebtSettings.DebtSettings.DebtFactor.

Reference

Debt Members
NDepend.TechnicalDebt Namespace