"A good shirt"
There was a mistake in the database.
crys (a shirt) is a masculine noun, and so there is no need to change da to dda.
(The changes to initial letters of some words in some circumstances are covered at various stages later in the course. One of these circumstances is that an adjective following a feminine noun needs to be softly mutated - don't worry if you have not heard the term before, as it is explained in the notes for a later section.)