Why it is still called sufficient: ability as such
Thesis XXVIII. The grace given to the others, in their view, is rightly called sufficient. Though it is not enough to give ability together with its effect, it is truly enough to give ability as such. No further aid is needed for those who have received it to be truly called able to do the works for which it is said to suffice, even though a fresh aid is needed for the action actually to follow.
That fresh aid does not add some new strength to the power, giving it ability in first act, as was said above. Its proper work is to move the power, already fit for acting, and apply it to the act.
Latin
XXVIII. Quae vero datur aliis, merito, juxta ipsos, dicitur sufficiens, quia licet non sufficiat ad dandum posse cum effectu, vere tamen sufficit ad dandum posse simpliciter. Nec enim ullum aliud auxilium necessarium est, ut qui illam acceperunt vere dicantur posse opera, ad quae sufficiens dicitur: quamvis opus sit novo auxilio, ut actio reapse sequatur. Nempe novum illud auxilium non superaddit potentiae novam aliquam virtutem, quae tribuat illi posse in actu primo, ut dictum est: sed proprium ejus est potentiam, quae jam ad agendum idonea est, ad actum movere atque applicare.