Per poncho's comment: the values given in the linked table are the number of multiplication or squaring operations in the finite field on which the Elliptic Curve is defined (which could for example be $\mathbb Z_p$ for some prime $p$); the cost of other operations in this field is either ignored as marginal (addition, subtraction, multiplication by a small integer constant) or absent (field inversion, which if present would account for 100).
The units are not in second, because counting field operations allows independence from both the speed of the hardware used, and the size parameter of the field (like $p$), which would influence the result in second. Know the duration of multiplication in your field using your device, multiply by the integer in the table, and you have some approximation of the duration for a sequential implementation.
ADD usually has more operations than DBL, because point addition on an Elliptic Curve usually turns out to be more computationally intensive than point doubling (as pointed by CurveEnthusiast in comment, that's not absolute): the later can be viewed as a special case of the former where the two inputs are equal, which allows a shortcut (or rather, requires it). As a crude analogy, it is slightly harder to compute $124865+138747$ than it is to compute $2\cdot124865$; for a start, there's more input.
