Da Capo is essentially same as the Dal Segno as if Segno is located at the top of the tune (implicit Segno).
When the tune is auftakt, the following rule is applied.
The bar length where Da Capo is located at the end of the bar is equal to the full bar length calculated by the tune's rhythm, play as if the implicit Segno is located at the beginning of the second bar (skip playing the first bar when goes back from D.C.).
Otherwise, play as if the implicit Segno is located at the top of the tune. The length of the first bar plus the length of the D.C bar should be equal to the full bar length calculated by the tune's rhythm.